In order to utilization of biogas slurry, this paper used a 3-years fixed site field experiment to study the effects of pig manure biogas slurry application on soil physical and chemical properties, and to assess the potential pollution risk of heavy metals in the soil. The planting pattern of the field experiment was rice-rape rotation, fertilization treatments included 2 controls of water and chemical fertilizer, and 10 application rates of pig manure biogas slurry. The indexes of single factor pollution, Nemerow pollution comprehensive and Hakanson pollution index of potential ecological risk were selected as evaluation indexes of the soil heavy metal pollution and potential ecological risk.The results showed that after 3-year application of biogas slurry in a total amount of(546.25~626.00)×10³ kg/hm²,the soil fertility and structure were significantly improved. It is worth to note that nitrogen fertilizer should be properly applied to cropland, in order to prevent soil nutrient imbalance. The contents of Cd, As, Pb, Cr and Hg were increased in the biogas slurry treated soils with an increasing application of biogas slurry. Furthermore, Pb, Cd, Cr, and As show slightly potential ecological pollution risk, and Hg exhibited a medium risk of potential ecological pollution, indicating biogas slurry can be safely used in agricultural production. This study indicates that the long-term application of biogas slurry is beneficial for the soil ecological function and the production of food security. Nevertheless,proper management of soil Hg and As is required to prevent soil contamination.