Nitrocellulose samples (NC) with A, B, C, and D grade were synthesized by nitrating Canadian softwood in HNO₃/H₂SO₄/H₂O and HNO₃/CH₂Cl₂, respectively. The nitrogen content and nitrogen content distribution (uniformity of nitration) of nitrocellulose were analyzed by a polarizing microscope. Using high-pressure steam explosion technology, soft wood was treated before processing. The effect of steam explosion treatment on the nitrogen content distribution of high nitrogen B and low nitrogen D grade NC was discussed. Results show that the nitrogen content distribution of nitration product from HNO₃/CH₂Cl₂ is more uniform than that of product from HNO₃/H₂SO₄/H₂O under the same nitrogen content condition. Uniformities of nitration indicators of NC of A, B, C and D grade improve by 16.9%、17.5%、16.8% and 25.7%, respectively. Steam explosion preprocess can improve nitrogen content and uniformity of product in the same nitrification system because the efficiency of nitration agents diffusion to cellulose fiber interior is improved by this treatment, and thus the uniformity for B grade NC can increase by 6.06% and for D grade NC by 7.56%.