Engraulis japonicus is a small warm-water pelagic fish commonly found along the coast of China. It is mainly distributed along the coasts of the East China Sea, the Yellow Sea, and the Bohai Sea, which are regions with abundant resources. Unlike adult E. japonicus, which is commonly used in the bait breeding market, juvenile E. japonicus can be dried and processed into a delicious and nutritious food, which has a higher market value. When E. japonicus spawns from April to June, fishermen along the coast of Zhejiang use nets and bag seines to catch juvenile E. japonicus. In 2018, the closed fishing season in the East China Sea begins from May 1 instead of June 1. In order to develop and utilize fishery resources rationally, the Ministry of Agriculture and Rural Affairs implemented special fishing concessions for this fishery, and local fishery administrative departments introduced and implemented a scientific observation system for this fishery. This study aimed to analyze the quantitative distribution of juvenile E. japonicus and its relationship with environmental factors. Scientific observation was conducted from April to June 2019 and the fishing activities of juvenile E. japonicus were recorded. The environmental factors were selected using Pearson’s correlation analysis to determine whether they were significantly correlated and to verify that the variables in the model were independent. Thereafter, the best model was determined by a minimum Akaike information criterion (AIC). The results indicated that the relative abundance of juvenile E. japonicus exhibited monthly variations, with the highest relative abundance in May and the lowest in April. GAM analysis revealed that the main factors influencing the resource density and distribution of juvenile E. japonicus were latitude, salinity, chlorophyll and dissolved oxygen along the Zhejiang coast. There was a multi-peak nonlinear relationship between the resource density of juvenile E. japonicus and the latitude, salinity at 0.5 m water depth, and dissolved oxygen at 0.5 m water depth. There was a positive linear relationship between chlorophyll at 0.5 m water depth and the resource density of juvenile E. japonicus. The results of this study provide a basis for the special concession fishing management of juvenile E. japonicus along the Zhejiang coast, and also provide a reference for resource assessment and study of adult E. japonicus.