Through the analysis of hydraulic-mechanical transmission and the modeling of torque converter, the traction performance of an automatic transmission car between hydraulic transmission and mechanical transmission under different throttle angle and different gears is discussed, and the control rule among dynamic gear-shifting, economic gear-shifting and mixed gear-shifting is made. Furthermore, the control strategy of engagement, disengagement and slip-control of lock-up clutch is set down. Simulation of integrated control of hydraulic-mechanical transmission which applies slip-control under multi-load-condition is carried out, and the result shows that the fuel economy of such type of the car gets an increase by 2.36%.