Chub mackerel (Scomber japonicus) is an important commercial fish species in the East China Sea and Yellow Sea. Since 1997, the annual catch of Chub mackerel has been decreasing. It is necessary to assess its stock size and manage it properly. The stock assessment and risk analysis of the management strategy for Chub mackerel was carried out using a Bayesian surplus production model, and the stock status was determined. The stock biomass, annual total allowable catch and probability that the stock collapsed in the next 5 years were also estimated. The results indicated that the stock of Chub mackerel in the East China Sea and the Yellow sea was in the state of “overfishing”, but not overfished in 2006. The decision analysis showed that harvest rate of 0.3 was the optimum management regulation with precautionary approach, under this harvest rate the average stock biomass would increase from 451 thousand tons in 2006 to 871 thousand tons in 2011, the probability that stock biomass in 2011 reaching BMSY would be 0.47, and the probability of having an overfished stock would be 0.