Abstract: Planned fire was implemented on May 4, 2014 at poplar plantation in Nanjing, Jiangsu province. On May 3 and May 5 of the same year, soil samples were collected in the same place to analyze instant variation of soil organic carbon and available nutrients before and after planned fire. The result showed that 24 hours later of planned fire, soil pH value, available phosphorus and potassium contents decreased with the deepness of soil layer, but increased with the intensity of fire. Soil organic carbon content decreased with deepness of soil layer. Soil hydrolysable nitrogen content decreased at 0-5cm and 5-10cm layers under the high-intensity fire, as well as at 0-5cm layer under the moderate-intensity fire. The experiment demonstrated that fire intensity had positive relation with pH value, available phosphorus and potassium, and negative one with organic carbon content.