Abstract: In recent years, praziquantel has been known to be a new and effective widespectrum antiparasitic. It is particularly effective in the treatmant of Schistosomiasis japanica infection.The high performance liquid chfomatographic method (HPLC) introduced in this paper for the determination of plasma concentration of praziquantel so far has not yet been reported. The specificity of the method was high and the limit of detection was found to be 20 ng,The metabolite distinctly appeared five minutes after intravenous injection to rabbits and was separated chromatographically. The mean value (n=7) of K_α=3.00 h^-1,t_1/2(α) = 0. 23 h, k_el,=0.28h^-1, t_1/2(β)=2.48 h. This indicates that the drug was metabolized quickly.Following oral administration of tablets or capsules of praziquantel to rabbits (n=13), the time reaching maximum plasma concentration (t_m)was found to be about one hour. The relative bioavailability of capsules was 74.8% that of tablets (0.011/2(β) of the tablets was longer than that of capsules, so the tablet of praziquantel used in clinics may be considered reasonable at present.