The synchronization of the unified chaotic systems using occasional driving technique is studied. The relation among interim periodT, sampling interval 2e, feedback gainr and the parameter α of the system is thoroughly investigated. Numerical results show that smaller interim periodT and properly larger sampling interval 2e can accelerate the synchronizing pace, Furthermore, for a unified chaotic system in which α is given, we can achieve satisfying synchronizing results as long asT,e andr are appropriately chosen. As we adopt the occasional driving method, we greatly reduce the control cost. Therefore with this method we can obtain the expecting goals with little control cost.