Chub mackerel (Scomber japonicus) in the East China Sea and Yellow Sea is one of the major commercial pelagic species in China, and its resource status and exploitation potential are receiving increasing attention. Strengthening the stock assessment research is the premise and foundation of the scientific management and sustainable utilization of chub mackerel. In this paper, a Bayesian biomass dynamics model was used to assess the chub mackerel. The catch data from 1979 to 2019 used in the assessment are from six provinces and two cities (i.e. Fujian, Zhejiang, Shanghai, Jiangsu, Shandong, Hebei, Tianjin and Liaoning) in China, Japan and Korea, and the resource abundance index data are from relevant references. Our results show that the prior distribution of intrinsic rate of increase (r) affects the parameter estimate of the model due to a strong negative correlation between r and carrying capacity (K) and a reasonable prior for r is helpful to improve the estimation quality of the model; the observation error precision of the catch data has an important impact on the estimates of the parameter and resource status; because the delineation of population structure of chub mackerel in the East China Sea and Yellow Sea is still controversial, it is currently not possible to separately evaluate each stock, and the stock assessment according to the statistical units is not conducive to the sustainable utilization of chub mackerel; chub mackerel has a high probability (>60%) of being overfished or being subject to overfishing; if the TAC (Total Allowable Catch) is below 4.82×10⁵ t, the probability of the stock not being overfished and not undergoing overfishing is expected to be greater than 60% in 10 years. Due to the current controversial status of the population classification of chub mackerel in the East China Sea and Yellow Sea and the difficulties in collecting corresponding data, we suggest that the stocks in the East China Sea and Yellow Sea be treated as one stock to meet the basic assumptions of the stock assessment model and to improve the quality of stock assessment. It will be beneficial to the sustainable utilization of chub mackerel if the catch is below 4.82×10⁵ t.