Pointing errors can reduce the number of received signals. The influence of pointing errors on intersatellite optical communication systems is decreased by selecting an optimum laser beam divergence angle for optimizing link reliability in the presence of pointing errors. Given that bias errors are part of pointing errors, an analytic expression of link reliability is obtained in the absence of bias errors. By maximizing link reliability, an analytic expression of the optimum beam divergence angle can be obtained. Bias errors are considered in maximizing link reliability. The numerical results and analytic approximation of the optimum ratio of beam divergence angle to pointing errors for a desired bit rate are obtained. With the application of the designed optimum divergence angle for intersatellite optical communication systems, good system performance can be achieved even in the presence of pointing errors.