The application of nitrogen and silicon fertilizers has an important role in promoting the growth and development of plants. This study was designed to investigate the effects of application of exogenous silicon at different nitrogen levels on growth and nitrogen metabolism of pepper seedlings. Taking the pepper variety "Audrey" as the test material，using the matrix cultivation，four nitrogen levels of 3913.5 (N1)，2236.5 (N2)，1564.5 (N3)，0 (N4) kg/hm² and 2 exogenous silicon levels of 0 (S0) and 1.5 mmol/L (S1) were set up，and the two factors were completely randomly combined，a total of 8 treatments were used to determine the biomass，root morphology，and mineral element content，photosynthetic characteristics and nitrogen metabolism related enzyme activity. The results showed that: (1) The fresh weight and dry matter accumulation of pepper plants both increased gradually with the decrease of substrate nitrogen level，and silicon application treatments both significantly increased the fresh weight and dry matter accumulation under each nitrogen level. (2) N2 level was more favorable to the accumulation of N，P and Ca elements in the aboveground and belowground parts of pepper plants，which increased by 6.03%-23.97%，compared with N1 level，and after silicon application，the contents of macroelements in plants under different nitrogen levels increased，and the N2S1 treatment had the best effects，which increased significantly by 8.13%-45.10%. (3) Compared with other levels，N2 level significantly increased photosynthetic pigment content in pepper leaves，and silicon application significantly increased photosynthetic pigment content and photosynthetic capacity of pepper leaves under different nitrogen levels，of which N2S1 treatment had the highest content of chlorophyll a，chlorophyll b，and carotenoids in leaves，with values of 2.97，1.11 and 0.58 mg/g(fresh weight)，respectively. (4) The activities of nitrate reductase (NR)，glutamine synthetase (GS) and glutamate synthase (GOGAT) in pepper leaves reached the maximum at N2 level compared to Compared with the N1 level，the activities of GS and GOGAT increased significantly by 34.71% and 19.87%，respectively. The addition of silicon significantly increased the activities of enzymes related to nitrogen metabolism in leaves at all nitrogen levels. Among them，the N2S1 treatment increased the activities of NR，GS and GOGAT by 42.86% to 80.47%，compared with those of the N2S0 treatment. In conclusion，a 40% reduction in nitrogen application promoted biomass accumulation，photosynthesis and nitrogen metabolism in pepper seedlings，and the effect was further enhanced by the application of 1.5 mmol/L exogenous silicon.