This paper investigated the temperature dependence of the cryogenic small-signal ac performances of multi-finger partially depleted (PD) silicon-on-insulator (SOI) metal oxide semiconductor field effect transistors (MOSFETs),with T-gate body contact (TB) structure.The measurement results show that the cut-off frequency increases from 78 GHz at 300 K to 120 GHz at 77 K and the maximum oscillation frequency increases from 54 GHz at 300 K to 80 GHz at 77 K,and these are mainly due to the effect of negative temperature dependence of threshold voltage and transconductanee.By using a simple equivalent circuit model,the temperature-dependent small-signal parameters are discussed in detail.The understanding of cryogenic small-signal performance is beneficial to develop the PD SOl MOSFETs integrated circuits for ultra-low temperature applications.