Abstract: γ- Harmine(Ⅰ),’harmine(Ⅱ )and harmaline(Ⅲ )were isolated from PeganumHarmala L.( Zygophylaceae).Tests were conducted with mice to detect whether γ- harmine( a newcompound), harmine,harmof(Ⅳ)and harmalol(Ⅴ) are effective radioprotective compounds againstγ-ray irradiation, Intraperitoneal injection of the hydrochlorides of the four alkaloids 50～80mg·kg^-1×1 in NIH male mice 30～45 minutes before 8.6～9. 7 Gy whole body ⁶⁰Co irradiationsignificantly increased the survival effects(1. 33～2. 61)and 30-day survivai rate in comparison withcontrol mice.The results indicatethat γ- harmine exhibited relatively good radioprotective effect.γ-harmine is the first alkaloid isolated from a plant having ptotective effects against whole-body lethal irradiation in mice.