The effect of adding P and Cd respectively or together on N mineralization in cultivated red soils derived from different parents (quater-nary red soil, weathering product of granite, weathering product of limestone, weathering product of slate), in Hunan, was studied based on indoor incubation with P concentrations of 0, 0.1, 0.3, 0.5 g/kg and with Cd concentrations of 0, 0.5, 1.0 mg/kg. Results showed that the average accumulation of N mineralized in quaternary red soil increased first and then decreased with the addition of P, and the maximum N mineralization was happened when the concentration of additive P was 0.1 g/kg. Average accumulation of N mineralized in other red soils increased with the increase of P addition. N mineralization was inhibited by Cd in both quaternary red soil and limestone red soil treated with Cd in a concentration range of 01.0 mg/kg, and the largest decline of N mineralization were 4.98 mg/kg and 6.53 mg/kg. Adding the P and Cd together promoted N mineralization in the red soils except the quaternary red soil, and N mineralization were different in red soils derived from different parent soils. Organic N in the red soil with slight Cd pollution mineralized most effectively under the P concentration of either 0.3 g/kg or 0.5 g/kg.