Excessive nitrogen application has been a major problem in corn production, and combined application of nitrogen fertilizer synergist can be used as an important technical measure to achieve high and stable corn yield under the condition of nitrogen reduction. In 2016 and 2017, field experiments were set up in Xinjian Village, Hexing Township, Zhongjiang County, Deyang City, Sichuan Province, to study the effects of different nitrogen application rates and nitrogen fertilizer synergists on soil available nitrogen content and dry matter accumulation and yield of corn, so as to provide scientific basis for reducing nitrogen and increasing yield cultivation techniques of corn. The results showed that the nitrogen reduction combined with synergist could enhance the supply capacity of available nitrogen in soil, promote the accumulation dry matter of corn, improve the yield composition, increase corn yield, and achieve nitrogen reduction without yield reduction. The yield increase ranges of the conventional nitrogen treatment and 20% nitrogen reduction combined with synergist treatment were 5.53%~13.97% and 10.24%~17.05%, respectively. The yield increasing effect of nitrogen reduction combined with synergist was better. Under the condition of reducing nitrogen by 20%, compared with A₂B₂ treatment and A₂B₃ treatment, urease activity and soil nitrate nitrogen content of the A₂B₄ treatment decreased by 19.00%, 15.65% and -2.97%, 57.24%, respectively, and the soil ammonium nitrogen content and yield increased by 11.48%, 248.50% and 3.71%, 6.18% on average in the two years. In summary, under the condition of reducing nitrogen by 20%, the combination of nitrification inhibitor (DCD) and urease inhibitor (HQ) had the strongest supply capacity of soil available nitrogen, which could reduce nitrogen application without reducing corn yield.