Root competition is one of the restricting factors of plant growth. Plants have different effects on nutrient cycling in rhizosphere during competition with respect to different root physiology and morphology, rooting systems and mixture composition. Rhizosphere is a hot spot with greatest enzyme activities that is affected mainly by roots of plants. Urease enzyme activity is an index of organic nitrogen mineralization and adjustment of nitrogen dynamics in soil. The purpose is to study the variation of absolute and specific urease activities on rhizosphere in pure and mixed planting of Quercus castaneifolia and Acer velutinium during different seasons. 18 rhizotrons were designed and assembled with sampling capability from different locations of rhizosphere and sequential times. Three planting treatments have five replicate while control have three. Results revealed that there were significant differences (p<0.05) of absolute and specific urease activities between different planting compositions and seasons. Absolute and specific urease activities increased 18.0% and 23.5% respectively in planting treatments from autumn 2015 to summer 2016. Mixed planting and control treatment have the most and the least absolute and specific urease activities respectively during all the studied seasons. Urease activity showed significant decrease in all treatments in winter. Mixed planting with two species have different rooting structure, created complementary ecological nests in the soil space, causing a significant increase in root biomass and urease activity on rhizosphere.