The pulsating heat pipe should have one eigen frequency based on the temperature visualization of pulsating heat pipe. The preliminary model of pulsating heat pipe is established by the force balance between the driving force, the inertial force and the frictional force. The results show that different structural parameter of pulsating heat pipe influences the eigen frequency differently. If a pulsating heat pipe has less turning number, or has micro or mini capillary, or has higher filling ratio, then the eigen frequency will change quickly. The frequency stands for the springiness of the system. The results can explain why some pulsating heat pipes with less turning number are hard to operate.