A 8-pole terahertz(THz) cavity bandpass filter with low insertion loss based on H ladder structure is presented. The filter is simulated and optimized by Ansoft HFSS, and it is finally processed by computer numerical control milling. The measured results show that the center frequency of the filter is located at 179.1 GHz with 1 dB fraction bandwidth of 8.4%. The insertion loss at 179.1 GHz is 0.34 dB, and the return loss is lower than 18.9 dB. The proposed THz cavity bandpass filter possesses the merits of low insertion loss, high selectivity and high stopband suppression, which can meet the requirements of THz communication systems.