During the Kofun period, a culture of horse riding was adopted by elites. We can recognize this phenomenon from horse trappings found in kofun burial mounds; however, we can find only fragments of such horse trappings due to corrosion. Horse trappings comprise fragments of cheek bits, strap unions, saddles, stirrups, crupper strap unions, and pendants. If we equip a horse with these parts, we must join them with many straps. These straps, known as gai 繋, are important in equipping a horse with various horse-related ornaments. However, in many excavations that found traces of horse trappings, corrosion and deterioration have left such straps barely recognizable. In recent years, archaeological observations have paid increasing attention to these little pieces of evidence that comprise metal parts, and we can now find clues that allow us to reconstruct both the techniques and materials that were used for horse straps during the Kofun period. However, such studies are sparse and few at present. This paper establishes a chronology and a means for the classification of horse straps. First, I examined the techniques and materials that were used for making horse straps. By examining many cheek plates, strap unions, crupper strap unions, and pendants, I was able to classify the two basic techniques used for making horse straps. One was through a double layering technique, and the other was through braiding. In the case of double layering, many supplemental decorative techniques were used such as, textile wrapping, rim decoration with stiches, supplementary stitching, wrappings with unidentified materials, and the attaching of decorated strings. Second, I classified the horse straps into 12 types by identifying different techniques and materials used. I further classified the double layering technique into nine types: normal, textile core, stitched, textile wrapped, stitched and textile wrapped, leather stitched strings, braided stitched strings, straps wrapped with unknown material, and those with decorative strings attached. Next, I classified the braiding of straps into two types: two-ribbed braided straps and four-ribbed braided straps. Third, I examined these various types of horse straps and identified which types of trappings they were joined to. This included cheek plates, strap unions, crupper strap unions, and pendants. The normal type was used from the 5th stage of the Middle Kofun period to the 1st stage of the Final Kofun period. It was found that they were joined to many types of cheek plates or pendants. For example, they were attached to f-shaped cheek plates, sword-shaped pendants, bells with pendants, palmette and phoenix-motif, heart-shaped cheek plates and pendants, and simple circular iron cheek plates. The stitched type was confirmed in three locations, such as the Kami- Enyatsukiyama Kofun 上塩冶築山古墳A. The textile-wrapped type was also confirmed in three locations, such as Bakuya Kofun 牧野古墳A. Stitched and textile-wrapped types were, however, confirmed in many locations. These were used from 7th stage of the Mjddle to 3rd stage of the Late Kofun period, and they were joined to f-shaped cheek plates, sword-shaped pendants, cross-motif oval cheek plates, three-leaf oval pendants, bell-shaped cheek plates, and bell-shaped pendants. Leather-stitched strings were confirmed in three locations, such as Takehara Kofun 竹原古墳b. Braided-stitched strings types were confirmed on only in Fujinoki Kofun 藤ノ木古墳A. Meanwhile, string-wrapped with an unidentified material type was confirmed in Takehara Kofun 竹原古墳a. Decorative string-attachment types were confirmed in Tamakiyama No.3 tumulus 珠城山3号墳 etc. This type was used during the 3rd and 4th stages of the Late Kofun period. On the other hand, two-ribbed braided straps were confirmed in many locations. For example, in the case of Kamo-inariyama Kofun 鴨稲荷山古墳, it is possible to recognize cross-motif oval cheek plates and three-leaf oval pendants. In other cases such as that of Ipponmatsu N