Abstract: The N-fixing property of 9 bacteria with N-fixation and disso lving P function was studied under the conditions of non-nitrogen，different P resources with sufficient nitrogen and their mixed ncubation．The results show that there are different N-fixation activities under the non-nitrogen condition，however，the volume of N-fixation has more dixrersity．The bacteria with the highest N-fixation amount is N5-1．reaching 55．4mg／kg and 3.l times as much as the lowest“K10-2”．When taking Ca₃(PO₄)₂ as P resource，“K10-2”and“N17”still have an active N-fixing ability under sufficient nitrogen supplied．the increasing range of total nitrogen in the culture,solution gets to 55．2％ after 3 days incubation．The N-fixation content of“N1l”，“N12”，“P14-2”als J maintain on a higher level，the total nitrogen increases by 30％ or so．The total nitrogen of“K16”in the culture so lution has a little increase．“N5-l”,“N 13-1”and“K3”result in the volatilization loss of nitrogen These processes will be reserved when taking the ground phosphate rock as the P-re-source．Compared to the single culture，the mixed incubation on Ca₃(PO4)：medium can effectively decrease N-loss of“N5-l”,“Nl3-l”,and“K3”．