This paper studies the vehicle formation cooperative control strategy in the case of coexistence of connected and autonomous vehicles (CAVs) and human-driven vehicles (HDVs) in a mixed traffic environment. An improved controller design approach is proposed in the context of CAVs with second-order models and HDVs with intelligent driver models (IDM). This enables CAVs to not only maintain following behavior with the vehicle ahead but also actively guide the rear vehicle's movement, which improves the previous state where the CAVs only take the role of followers. We first construct a mixed vehicle formation model to convert the formation control problem into a leader-following consensus problem, after which we design a control protocol and solve the formation consensus problem using state linear transformation and partial stability theory. Finally, the solution method of the gain matrix in the control protocol is given, and the effectiveness and superiority of the controller are verified through simulation.