The four determination methods(Olsen,Bary1,ASI and Mehlich3 methods)of available phosphorus for soil were used to determine available phosphorus in substrates of soilless culture.The results showed that there were not significant different between determination of available phosphorus by ASI and routine method(Olsen method)and significant differences exist for determination of available phosphorus by Bary1 and Mehlich3 method compare to Olsen method at α=0.05 significant level.Therefore,ASI method was suitable for determination of available phosphorus in substrates of soilless culture.