Abstract: In space environment,radiation may induce the leakage and capability degeneration of power management circuits.Compared to CMOS,LDMOS has higher working voltage,so it is widely used as large size power transistors in power management circuits. In this paper,total ionizing dose(TID) radiation effects of LDMOS are studied in a 0.25 μm BCD process. TID radiation induces LDMOS threshold voltage shifts and, in n-channel straight gate LDMOS, leakage current. The p-channel straight gate transistor's leakage current caused by TID radiation is also observed and recorded. ELT hardening technique can effectively limit the radiation-induced eage leakage of n-channel LDMOS. When radiation dose is 100 krad(Si),the threshold voltage shifts of n-channel ELT LDMOS and p-channel straight gate LDMOS are respectively 0.02 V and -0.02 V.