This paper presents a well-performance 90° differential waveguide phase shifter with corrugations on the opposite two-walls for the Q-band cryogenic receiver on the Tianma telescope. As the key component combining with the feed horn and the orthomode transducer, which receives the radio astronomy waves and splits left-hand and right-hand circular polarization signals, it works at a 15-20 K platform to lower down the noise contribution to the receiving system with maximum sensitivity. The measured results show that insertion losses of the differential phase shifter for both polarizations are less than 0.1 dB. Excellent return losses at the output ports of the differential phase shifter better than 17 dB, and axial ratio less than 1 dB in the 35-50 GHz are obtained, which agree well with the simulation results.