Before revision:  This paper aims at solving this kind of the optimal problems, that is, working out the optimal control policy of the insurance company , in particular, exact minimum dividend barrier, and finding the optimal return function associated with the optimal policy .
After revision:  This paper aims at solving this kind of the optimal problems, that is, working out the optimal control policy of the insurance company . As a by-product, the paper also sets a risk-based capital standard to ensure the capital requirement of can cover the total given risk, and the effect of the risk level on optimal retention ratio, dividend payout level and optimal control policy are also presented .