To identify the causal agent of gray leaf spot on Solanum lycopersicum and to screen for effective control measures, the pathogen was characterized through morphological observation, pathogenicity test and phylogenetic analysis, and the field efficacy of 19 fungicides against this disease was evaluated. The results showed that the isolated pathogen formed colonies that were yellow on the obverse and yellowish-brown on the reverse. The conidia were brick-like, with 1-3 transverse and several longitudinal septa. Based on the pathogenicity tests, as well as phylogenetic analysis of the ITS and GAPDH gene sequences, the pathogen causing gray leaf spot of Solanum lycopersicum in Jiangxi Province was identified as Stemphylium lycopersici. 65% zineb wettable powder(WP) showed the best control efficacy against gray leaf spot of Solanum lycopersicum with an efficacy of 71.35%, followed by 75% chlorothalonil WP with an efficacy of 68.77%. These fungicides could be used alternately in production to delay the development of resistance in the pathogen causing gray leaf spot on Solanum lycopersicum.