Abstract: ‘Red Dragon 23’ of the main pigmented pepper in Xinjiang was used as the test material.N0（no N application）,N100（full N）,N60（40% N reduction） and N20（80% N reduction） were applied at seedling, fruit set, fruit expansion and fruit ripening stages.The effects of N reduction on aboveground and leaf biomass and total N content in the latter four periods were studied, and a model was constructed to model the critical N concentration dilution curve of pigmented peppers, in order to provide reference for the precise management of nitrogen fertilizer for pigment pepper in Xinjiang.The results showed that the dilution curves of the critical nitrogen concentration of pigmented peppers were all in accordance with the negative power index relationship.The aboveground N content of ‘Red Dragon 23’ pepper at the seedling, fruit set and fruit set stages was around the dilution curve under N80 fertilization.This means that these three periods could be reduced by 20% on the basis of the traditional N fertiliser dosage; however, the NNI was mostly below 1 during the fruit ripening period due to the rapid dilution of N,so a reduction in N fertiliser dosage was not recommended for this period.