Abstract: In this paper, we consider the optimal joint dividend and capital injection strategy with proportional and fixed costs. It supposes that capitals can be injected whenever they are profitable, but dividends can only be paid at the arrival times of a Poisson process with intensity . Our objective is to determine an optimal strategy of maximizing the expected cumulative discounted dividends minus the expected discounted costs of capital injections before bankruptcy. By solving some impulse problems, we get the closed-form solutions depending on the parameters of model. Some known results in Lokka and Zervos (2008) can be viewed as limiting cases when .