The utility model discloses a chain and a chain plate unit thereof. The chain comprises a plurality of chain plate units which are arranged along the length direction and a plurality of chain shafts which are in tandem connection with the adjacent two chain plate units; every chain plate unit comprises two chain plates which are arranged internally and externally; the chain plates are arranged in an inwardly staggered or outward alignment mode; one chain plate is provided with a large protruding column and a large penetration hole; the other chain plate is provided with a small protruding column which can penetrate the large penetration hole and a small penetration hole which is for the chain shafts to penetrate. The chain and the chain plate unit thereof have the advantages of saving a bush and a chain roller of a traditional chain and achieving purposes of simplifying necessary components, reducing assembling costs and assembling steps.