The invention provides a ball joint and a connection unit consisting of the ball joints, wherein the ball joint comprises a ball seat, a ball body and a clamping ring which are made of a resin material with both elasticity and rigidity; the ball seat comprises a ball socket, and the ball body and the ball socket are rotatably matched; pits and protrusions which are mutually matched and regularly distributed are formed on the inner surface of the ball socket and the outer surface of the ball body; an annular groove is formed on the outer surface of the ball seat; and the clamping ring and the annular groove are matched so as to limit the ball body in the ball socket. Because the pits and the protrusions which are mutually matched and regularly distributed are arranged between a ball head and the ball socket, the ball body can do cadent rotation, and the matching between the ball body and the ball socket is not easy to slide.