This paper mainly investigates the total dose irradiation effects on 0.8 μm PD SOI PMOS devices which are exposed to 60Co γ-rays at a dose rate of 50 rad(Si)/s. The channel length dependence of SOI PMOS devices at total dose irradiation is investigated. The result shows that the threshold voltage shift is only a little larger for shorter channel devices at the same total dose. However, the degradation of maximum transconductance for shorter channel devices is more significant. We found that the oxide-trapped charge is the main factor impacting the threshold drift. We may conclude that a short channel device can produce more interface trapped charges by using the subthreshold separation technology.