Abstract: The effect of pig slurry on the availability of heavy metals depends on soil pH. In the present study, three soils with pH of 3.62 (acidic), 7.23 (Neutral) and 7.85(alkaline) were used to investigate the availabilities of Pb, Cu and Zn when adding the pig slurry from anaerobic fermentation process in a large pig farm. The results showed that under low dosage of slurry (1 350 m3 / hm2), the exchangeable content of Pb and Zn in the three soils decreased by 50.3% ~ 78.9% and 55.1% ~ 76.0%, respectively (P <0.05). The content of exchangeable Cu in acidic and alkaline soils was significantly reduced, with a decrease of 87.7% and 80.8%, respectively. The decrease in the exchangeable Pb and Cu contents corresponded to the increase of the oxidizable and residual fractions. But for Zn, the decrease in the exchangeable fractions corresponded to the increase in the reducible and residual contents. In contrast, under the high dosage of biogas slurry (2 700 m3 / hm2) the exchangeable Pb and Cu fractions in all soils increased by 31.0% ~ 122.2% and 84.6% ~ 101.7%, respectively. The exchangeable Zn fractions increased by 14.3% in acid soils and 46.1% in alkaline soils. Therefore, the effect of pig slurry on the availability of soil Pb, Cu and Zn mainly depends on its dosage. Low dosage of application helps reduce the availability of heavy metals while high dosage would increase the pollution risk. In the context, the impact of soil pH varies greatly among different heavy metals.