To provide smooth viewing experience, the design of continuous autofocus of video cameras needs to take the scene dynamics into consideration in the algorithm development and testing cycles. However, this is often a time-consuming and tedious process because it requires a huge amount of tests on various real scenes. We propose in this paper a simulation method to simplify the digital autofocus design process. This design-by-simulation method significantly reduces the development and testing time of the search strategy for digital autofocus. Experimental results are shown to demonstrate the effectiveness of the proposed method.