Under the condition of urea fertilization, the hydroquinone (HQ), as a urease inhibitor, was applied to postpond the hydrolysis of urea for decreasing the volatilization of ammonia and restraining its nitrification. As a protective measure of urea fertilization, HQ was very effective in alleviating the inhibition effect of urea fertilizer on the symbiotic nitrogen fixation System of soybean. HQ was found to have no unfavourable effect on the growing of the purecultured soybean rhizobia, the growing of the seedings of soybean and primary forming of the nodules at an applied levels of HQ. Furthermore, the respiratory activity of isolated-cultured active root nodule and the activity of succinic dehydrogenase were promoted remarkably. Under pot and field conditions, fertilizing urea with HQ, compared with check (no HQ), could notably raise the nodule quantity and increase the total nitrogen fixation activity of single plant and enhance the content and relative abundance of ureide nitrogen in plant hadromestome of soybean. Therefore, fertilizing urea with HQ could improve the development of the soybean symbiotic nitrosen fixation system and coordinate the supply of the nitrogen sourced from nodule or soil (fertilizer) needed by soybean. Thereby, the rich nitrogen could be provided for synthesizing protein of seed. For this reason, fertilizing urea with HQ could increase soybean yield very remarkably.