A microbial library of Qingzhuan brick tea with pile-fermentation was screened with neutral red-olive oil plate assays and an improved copper soap method to study the effects of lipase-producing strains on the content of fatty acids in the fermented tea and analyze the mechanism of forming flavor quality in Qingzhuan tea.17 strains of bacteria and 19 strains of fungi capable of producing lipase were screened from the microbial library of Qingzhuan tea.Among them， N8.11-20 strain had the highest activity of lipase （7.82 U/mL） and was identified as Pseudomonas aeruginosa.The results of optimizing the culture conditions for producing lipase with single factor experiments showed that the optimal culture conditions for the activity of lipase in N8.11-20 strain are an inoculation volume of 6% （V/V）， a culture temperature of 34 ℃， an initial pH of 7.0， and a culture time of 72 hours.The content of oil in Laoqing tea fermented with N8.11-20 strain for 15 days increased from 12.22% to 15.37%， which increased the content of total fatty acid in the fermented tea.It is indicated that using lipase-producing strains to ferment dark tea can help improve the aroma quality of dark tea.