Effects of earthworms on soil nitrogen mineralization were studied in laboratory.Soil samples were destructively collected periodically on D2,D6,D13,D20,D27,D41,and D55 after incubation.Four treatments were designed:(1)soil without earthworms or straw-control treatment(S);(2)soil only with earthworms(E);(3)soil only with straw(O);and (4)soilwith earthworms and straw(OE).Results indicated that throughout the entire incubation period,only Treatment Ewas significantly higher than Treatment S(p<0.05)in both NH₄⁺-N and NO₃^--N,by about 0.54～5.71 and 0.04～2.01 times separately.Compared with Treatment O,Treatment OE was much higher(p<0.05)in content of soil NH₄⁺-N,by about 0.42～7.26 times.but was more or less similar(p>0.05)in content of soil NO₃^--N.Whether the straw was used or not,Treatments E and OE were significantly higher,or 1.93 and 2.36 times higher than Treatments S and O in content of mineral nitrogen (NH₄⁺-N+NO₃^--N),respectively,after 55 days of incubation.The soil nitrogen mineralization rate and cumulative nitrogen mineralization rate in Treatment E increased significantly(p<0.05)over Treatment S;In Treatments O and OE,whether earthworms were introduced or not,the cumulative nitrogen mineralization rates were below zero,represented as net immobilization of soil mineral nitrogen,and change in nitrogen mineralization rate showed net immobilization in the early phase,and certain mineralization in the late phase.The content of total nitrogen in Treatment E was significantly higher(p<0.05)than in Treatment S in all the incubation phases except for in the first 2 days of incubation and at the end of the experiment,it was about 6.55% higher.Besides that,significant positive correlation(p<0.01)was observed between soil total nitrogen content and decrement of earthworms in fresh weight.When the loss of earthworms in fresh weight was converted into the loss of nitrogen through earthworms with the simple liner equation,it was found that the nitrogen excreted by earthworms accounted for about 42%～100% of the increment of soil total nitrogen.