To analyze factors influencing the determination of nitrate in soils,the effects of sample preservation method,extracting agent,analysis method,purity of water and chemical reagents on the determination of nitrate in three typical soils including black soil,alluvial soil and red soil,were investigated.The results showed that the cryopreservation method was better than the cold preservation for the collected soil samples.Analysis of nitrate in soils kept in freezing and cooling conditions should be finished within 45 d and 7 d,respectively.There were no significant difference between 0.01mol/L CaCl2 and 2 mol/L KCl used for extraction of nitrate.No significant difference was found in analyzed results between the standard method for forestry soils (LY/T 1230-1999) and the UV spetrophotometry,whereas values of UV spetrophotometry were significantly higher than that of the continuous flow injection analysis method,and an obvious correlation was found between them.The use of impure water would make results higher,techniques with respect to boiling,distillation,and distillation for ammonia removal of water could eliminate the effect of impurity.