Inverter compressor operating in low frequency range shows apparent speed fluctuation． It is the periodic load torque disturbance that brings about speed offset． The poor performance of periodic load disturbance is caused by the small gain of disturbance observation ( DOB) ． To solve this problem，a periodic disturbance observer ( PDOB) was proposed to estimate load disturbance and compensate current in this paper and attenuate speed deviation in low frequency range． Load disturbance is compensated by PDOB based on internal model theorem，including fundamental and related harmonic components． Adaptive notch filter based on Steiglitz-McBride method was constructed to estimate the fundamental frequency of periodic disturbance． Experiments were carried out on inverter compressor platform and results show that speed fluctuation of can be effectively suppressed by the proposed method comparing with general DOB．