Objective Methods Rats of model groups were given silaenafil 10mg / kg by gavage． Rats of control groups were given normal saline only． All rats were gavaged once a day for two weeks． Rats were observed for 2 hours after each drug administration for penile erection，genital grooming and possible copulation mounting． The number of responding rats was recorded along with the number of sexual activity episodes ( penile erection，genital grooming or copulation mounting) ． Penile erection index ( PEI) was calculated for each group by multiplying the percentage of active rats ( responding rats) by the total number of activity episodes． By using the modified assessment method，male rats were observed by camera． Meamwhile，we also stimulated the male rats by female rats at different periods． Results Among female rat-stimulated groups，the model groups compared with the control groups，PEI was significantly increased ( P＜0. 05) ． Among the model groups，the camera observed group compared with the human observed group， PEI was significantly increased ( P＜0. 05 ) ． Compared with non-female rat-stimulated group，PEI was significantly increased in female rat-stimulated group( P＜0. 05) ． The 2 h PEI showns no significant differences between sustained induction group and intermittent group． But，during the period of the second hour，PEI was significantly increased in intermittent group ( P＜0. 05 ) ． Conclusions After optimized，the assessment methods can evaluated the strengthening yang efficacy of candidate drugs more effective．