Abstract: As a new type of guided wave structure, SAFSIW (Slab Air-Filled Substrate Integrated Waveguide) is widely used in the design of millimeter wave transmission lines and passive circuits. Compared with the traditional SIW structure, SAFSIW has higher Q value due to the existence of air gap. In this paper, a compact band-pass filter is designed based on the half mode double cavity coupling SAFSIW. By connecting the stub line structure in parallel in the resonator, a transmission zero is introduced in the upper band of the filter, which greatly improves the out of band suppression characteristics of the filter. The filter is implemented by LCP process and tested. The measured results show that the center frequency of the filter is 19 GHz, the fraction bandwidth is 18%, the insertion loss is better than -4.2 dB, and the return loss is below -16 dB. Due to the introduction of transmission zeros in the upper sideband of the filter, the upper sideband suppression is below -36 dB at 28.5 GHz. The measured result of the fabricated filter has a certain deterioration compared with the simulation result, mainly due to the loss caused by the SMA connector and the machining error of the HMSAFSIW resonant cavity.