Heat pump system can save energy and installation cost and reduces CO2 emissions. In cooling overload region such as vary hot weather, the release control for system protection and capacity control operate at the same time, and therefore the system stability of heat pump is decreased by a hunting phenomenon in heat pump system. In this study, we developed cascade PID control for heat pump that can be controlled the system protection and capacity at the same time. In this study, a system identification of an air source heat pump using R410A with a variable speed compressor was experimentally investigated under various ambient and indoor temperature and cooling capacity. A heat pump system was installed and tested in an environment chamber, where temperature and humidity are precisely controlled. We developed output range model and dynamic characteristics factor (gain, time constant) of control variable for cascade PID control using a system identification experiment data. In this study, cascade PID control for heat pump was developed using developed output range model and dynamic characteristics factor. Performance analysis of the developed cascade PID control was performed compare with the existing control by experimental study that change control objectives.