In order to obtain actuator placement optimization for the spatial truss stucture，this paper constructs the active vibration control system of spatial truss structure based on linear quadratic regulator （LQR） optimal controller theory， and maximizing the modal damping of the target control mode is proposed as the actuator placement optimization criterion. The effectiveness of the proposed method is verified by using the square pyramid space grid structure and the Levy-type cable dome structure， and the control effect and energy input are compared with those of the existing method. The comparison results show that with the increase of the number of actuators， the control effect and control energy input of the proposed method tend to stabilize faster than that of the existing method； when the number of actuators is the same or the energy input is the same， the control effect of the proposed method is better than that of the existing method.