In order to analyze the effects of nitrogen fertilizer and varieties on the agronomic traits and yield of sweet sorghum，four varieties [LiaoTian 3 (A)，LiaoTian 1 (B)，Dalishi (C) and 3701 (D) ] were used as the materials in this experiment，and four nitrogen application treatments were set up (CK:N 0 kg·hm-2，N1:N 34.5 kg·hm-2，N2:N 138 kg·hm-2 N3:N 241.5 kg·hm-2)，and the related indicators such as agronomic traits，sugar content，chlorophyll，and yield of straw in five periods [division stage (S1)，nodulation stage (S2)，tassel stage (S3)，milky stage (S4) and maturity stage (S5)] were determined. The variation pattern and correlation analysis between yield and yield composition factors was analyzed. The results showed that from division to maturity stages，varieties had a significant impact on the law of change of sweet sorghum moisture，chlorophyll，plant height，stem thickness，number of leaves，sugar content and fresh weight of single plant in the varieties and nitrogen treatments. The growth was rapid from the tillering stage to the tasseling stage，while it changed slowly from tasseling stage to maturity stage，and reach the maximum value in the maturity stage. Application of nitrogen，varieties and the interactions of nitrogen applications with the varieties significantly (P<0.01) affected plant height，stem diameter，sugar content，moisture content，dry matter content，fresh weight per plant，thousand grain weight，grain and biomass yield in maturity stage. The fresh weight per plant，biomass yield and thousand grain weight of the four varieties increased with the increase of nitrogen application，and under the same nitrogen application conditions，the biomass yield was in the order of C＞A＞D＞B，and the nitrogen fertilizer utilization efficiency ranged from 11.74% to 27.68%，of which varieties A，B and D showed significantly higher nitrogen fertilizer utilization efficiency in the N2 nitrogen fertilizer utilization efficiency range. The nitrogen fertilizer utilization efficiency of varieties A，B and D was significantly higher than that of other treatments in N2，and variety B had the highest nitrogen fertilizer utilization efficiency (27.68%). In summary，the amount of nitrogen application and varieties had a significant impact on the growth，yield and nitrogen fertilizer utilization of sweet sorghum，but excessive application of nitrogen fertilizer led to the reduction of nitrogen fertilizer utilization and increase in economic inputs. For variety B，nitrogen fertilizer dosage of 138 kg·hm-2 was conducive to the improvement of the efficiency of nitrogen fertilizer utilization，and variety C，as a preferred high-yield and high-quality varieties， 241.5 kg·hm-2 nitrogen application was conducive to the high yield. Therefore，it was more scientific and reasonable to choose variety B or C for planting in this area.