Aimed at the requirements of automatic and continuous operation of big square straw bale collecting and stacking machine, the hydraulic control system of big square straw bale collecting and stacking machine is developed. The designs of loadsensitive control, clamping and turning loop control and load balance control were used in the hydraulic control system. The system had the characteristics of simple layout, good operability and high reliability. The actual application results show that the heat of the continuous operation of the system is reduced and the automatic operation level is improved effectively.