The crossover conveyor chain system includes a first conveyor chain (S1) and a second conveyor chain (S2) crossing the first conveyor chain (S1) to transfer the product from the first conveyor chain (S1) to the second conveyor chain (S2) while reorienting the product to a direction nearly perpendicular to that on the first conveyor chain (S1). The first conveyor chain (S1) is supported on an end bar (10) or a small-diameter sprocket, and the second conveyor chain (S2) is formed a plurality of chain unit pairs each including at least two types of chain units (A) different in length from each other and a coupling pin (B). Each of the chain units (A) has front convex portions (1) and front concave portions (3), disposed alternately at the front thereof, rear convex portions (2) and rear concave portions (4), disposed alternately at the back thereof, and a transfer overhanging portion (7) formed integrally at one lateral thereof. The transfer overhanging portion (7) has a beveled lower surface (8) formed on the lower side, at the free end, thereof and an inclined upper surface (9) formed on the upper side, at the free end, thereof. Because of this construction, the transfer overhanging portion (7) can be set short, and so it can be formed not easy to flex and break as well as to flex vertically, which assures to transfer the product stably and smoothly and prevent the load (weight) of the product from concentrating on a limited portion of the conveyor chain. Therefore, the crossover conveyor chain system is highly strong, rigid and durable, easy to be designed lightweight and compact, simple in construction, suitable for mass production, easy to assemble, easy to handle, and less expensive.