The band pass filter is an important component of the rendezvous parameter millimeter wave detector, and its performance directly affects the detection ability of the detection signal.Its performance directly affects the detection ability of the detection signal. According to the design requirements of millimeter wave detectors, a design scheme of bandpass filter based on loaded stub T-type resonator is proposed. On the basis of calculating the resonant frequency of the resonator and the structural size of the filter,According to the dual-mode stepped impedance resonator model, a microstrip bandpass filter with a center frequency of 36GHz and a bandwidth of 1GHz is obtained through branch loading, combined with HFSS software modeling and simulation optimization.The simulation results show that the band interpolation loss of the millimeter wave narrowband filter is less than 3dB, the in-band return loss is greater than 20dB, and the stopband attenuation is greater than or equal to 20@35.5GHz and greater than or equal to 20@36.5GHz,Basically meet the requirements for the use of millimeter wave detectors.