On the basis of seven long-term located experiments in paddy fields,analysis was made on the change of heavy metal content and its availability in soil of 0~20 cm which were treated with four different fertilization trails detailed as fertilizing by no fertilizer,NPK,middle-level manure(30% organic N 70% chemical N) and high-level manure(60% organic N 40% chemical N).The results indicated that there was a bigger risk for paddy soils to be polluted by heavy metals under the treatment with long-term combination of chemical fertilizers and farmyard manure.Little change happened on the contents of total and available Zn,Cu,Cd,Pb and their activity under NPK treatment.But total and available Zn, Cu,Cd contents and their activity significantly ascended under MOM or HOM treatment.The most increase was under HOM treatment,at a rate of 6.1%,18.7%,8.3% respectively for total Zn,Cu,Cd contents,at a rate of 87.3%,65.8%,41.4% respectively for available Zn,Cu,Cd contents,and at a rate of 77.5%,32.0%,29.8% respectively for activity of Zn,Cu,Cd,compared with CK treatment.This increase was mainly caused by "activation" effect of farmyard manure.In addition,soil total Cd content overtopped Soil Environmental Quality Standard II(0.30 mg/kg) in all experiment sites,indicating that there was possibly prevalent Cd pollution in these paddy soils.