To study the influence of porous copper dimension on its azide reaction, according to the different solubleness of copper azides and copper at 50 ℃ in 0.5 mol·L^-1 diluted hydrochloric acid, the reaction characteristics of copper particles with different sizes and monolithic porous copper with particle size of about 200 nm, thickness of 0.2-0.3 mm and density of 1.51 g·cm^-3 with gaseous diazoimide were analyzed by an ICP spectrometer. Results show that when the size of copper particle is about 0.5 μm, the average conversion of copper particle can reach 95.64%, the copper particle can react with gaseous diazoimide completely. When the thickness of porous copper is 0.2 mm, the conversion of the azide is greater than 97%.