This study is conducted based on the bottom trawl surveys in the Wenzhou-Taizhou area, off the waters of the southern Zhejiang. Survey data were collected from 2016-2018 in all four seasons:Early March(winter), May (spring), August (summer), and November (autumn). The generalized linear model (GLM) and 9 linear mixed-effect models (LMEM) were used to analyze the fork length-mass relationship (W=aL^b) and its heterogeneity for Pampus echinogaster.The results showed that the fork length of Pampus echinogaster in this region was from 53.00 mm to 238.00 mm, with an average fork length of 128.54 mm. The dominant fork length group was from 110.00 mm to 160.00 mm. The mass range was from 3.80 g to 420.50 g, with an average mass of 63.61 g. The dominant body mass group was from 60.00 g to 180.00 g. According to the Akaike Information Criterion (AIC), the best fitting model was the model with a combination of both seasonal and yearly random effects on the growth parameters a and b of Pampus echinogaster. The root-mean-square error results also showed that this model had the best effect. In the optimal model, the fixed value of parameter a was 1.75×10^-5, and the fixed value of parameter b was 3.083, which indicates that Pampus echinogaster follows a positive allometric growth and presents better condition. The results of the optimal linear mixed model showed that the largest value of a was recorded in autumn, followed by summer and winter, and the smallest in spring; opposite trend was obtained for parameter b. From different years, the value of a was the largest in 2016, followed by 2018 and 2017; the value of b was the largest in 2017, followed by 2018 and 2016. The annual and seasonal impact on the fork length-mass relationship of Pampus echinogaster is analyzed through the mixed effect model.It shows that the year and the season have significant effects on the fork length-mass relationship of Pampus echinogaster, and that the model has important reference value in the study of the heterogeneity for the fork length-mass relationship of Pampuse chinogaster, and provides a scientific basis for the rational development and management of its resources.