Abstract: In this article, a bandpass filter based on Half-mode Substrate Integrated Waveguide(HMSIW) is presented by inserting the fractal slot. By etching tree-shaped fractal slots in the HMSIW surface, the proposed filters can obtain wide stopband in the high frequency band. With the increase for iteration order, the filter has almost same fractional band-width(S11 <-15dB), and has the advantages of good roll-off slope and high out-of-band rejection without deteriorating the fundamental performances. The measured results are in good agreement with the simulated results, which shows that the design of the proposed filters is correct and effective.