A model of stirling heat engine was established on application of practical schmidt cycle theory. The influence of heat loss based on the pressure loss for the thermal efficiency of the stirling heat engine with the use of an instance of the solar stirling heat engine was analyzed particularly. Results indicate that heat conduction loss and shuttle heat loss are more amount than all kinds of heat loss and heat conduction loss is the most significant. A variety of heat loss is closely related to structural parameters and performance parameters of the stirling engine. Increasing the temperature of heat pipe wall and decreasing the speed value would improve cycle thermal efficiency. When the temperature of the heater is more than 750K, the value of cycle thermal efficiency of the solar stirling engine will be very close to 65%~80% Carnot efficiency approximately.