In order to explore the effects of nitrogen reduction combined with slow release nitrogen fertilizer on soil enzyme activity and nitrogen absorption and utilization in cotton field, the effects of nitrogen reduction and different proportions of slow release nitrogen fertilizer on soil physical and chemical properties, enzyme activity, inorganic nitrogen content, nitrogen use efficiency and cotton yield were studied. The cotton variety "Xinluzao 64" was used in the experiment. Two nitrogen application methods were set up:The conventional total urea (T2) and slow release nitrogen fertilizer combined with urea (US). The combined application treatments were set at three levels according to the nitrogen application rate, namely, no nitrogen reduction, U_0.8S_0.2 (T3) and U_0.6S_0.4 (T4) (the subscript values refer to the proportion of urea and slow release fertilier in the total nitrogen); nitrogen reduction of 20%, U_0.6S_0.2 (T5) and U_0.4S_0.4 (T6); nitrogen reduction of 40%, U_0.4S_0.2 (T7) and U_0.2S_0.4 (T8); and no nitrogen application (T1) as the control, with a total of eight treatments. The soil physical and chemical properties, enzyme activity, inorganic nitrogen content, nitrogen content and yield of cotton at different growth stages were measured and analyzed, and the nitrogen use efficiency was calculated. The results showed that compared with the conventional total application of urea, the combined application of slow release nitrogen fertilizer could significantly increase the soil water content and total nitrogen content. Among them, the soil water content of T4 was the highest, which was 14.07%, 11.05%, 7.58%, 6.22% and 6.65% higher than that of T2 at the seedling stage, bud stage, flowering stage, boll stage and boll opening stage of cotton, respectively. The soil total nitrogen of T4 was significantly higher than that of T2 at flowering stage, reaching 1.24 g/kg. There was no significant difference in soil urease activity, sucrase activity, catalase activity, alkaline phosphatase activity and ammonium nitrate content between the treatments of T5, T6 and T2 at each growth stage. The soil urease activity and nitrate content in the mature stage of the treatments of T5 and T6 decreased by 28.20%, 26.40% and 11.13%, 8.32%, respectively, compared with the T4. In addition, the nitrogen use efficiencies of T5 and T6 were significantly higher than that of T2, by 62.09% and 62.43%, respectively. But there was no significant difference in yield and its components. In summary, the soil enzyme activity, inorganic nitrogen content and yield of the treatment with 20% nitrogen reduction combined with slow release nitrogen fertilizer (T5, T6) were not significantly different from those of the conventional (T2), and the nitrogen use efficiency was significantly higher, which could ensure the nitrogen supply in the whole growth period of cotton, avoid the nitrogen waste, and achieve the purposes of high yield and efficient utilization of nitrogen fertilizer.