A pot experiment was conducted to study nitrogen content, related microorganisms and enzyme activities in tea garden soil under different lead (Pb) concentrations under accumulation and one-time addition. The results showed that the total and available Pb contents in soil under accumulation treatment were higher than that under one-time addition. The effects of Pb pollution increased the contents of total nitrogen and ¹⁵N in soil, but decreased the contents of total nitrogen and ¹⁵N in overground part of tea plant. When Pb concentration was 900 mg/kg, the contents of total nitrogen and ¹⁵N were promoted under accumulation treatments, and significantly decreased under the one-time treatments. The nitrogen contents in roots and shoots of tea seedlings under accumulation treatment was significantly higher than that under one-time addition (P<0.05). The effects of Pb pollution decreased the numbers of ammonifying bacteria, azotobacter, nitrite bacteria and nitrate bacteria, but increased the number of denitrifying bacteria. The number of microorganisms related with nitrogen cycling were not significantly affected by different Pb addition modes (P>0.05). Pb pollution inhibited the activities of urease, nitrifying reductase and nitrate reductase, and showed a phenomenon of "low promotion and high inhibition" on protease activity. When high concentrations of Pb (900 mg/kg) were added in soil, the cumulative treatment significantly increased the activity of soil hydroxylamine reductase, while one-time treatment significantly inhibited it. The effects of two pollution modes on soil urease, nitrate reductase and hydroxylamine reductase activities varied greatly depending on the concentration of Pb pollution. Correlation analysis showed that the number of microorganisms related to nitrogen transformation (excluding denitrifying bacteria), the activities of protease, nitrite reductase and nitrate reductase were significantly negatively correlated with the total and available Pb content in tea garden soil (P<0.01).