Software testing is the most time and resource consuming stage during software development. For series-parallel software systems, as the reliability of the system changes as the testing time advancing, if the strategy of testing resource allocating is still executed in accordance with the original plan, it may lead to a vast waste of testing resource. To address the issue, this paper tackles a testing resource dynamic allocation problem for series-parallel software systems with bounded resource in the field of search based software engineering. Firstly, the definitions of testing resource, system reliability and testing cost are given. Based on these definitions, a multi- objective dynamic allocation model for testing resource is established with the objective of allocating the testing resource among different modules to maximize the reliability and minimize the testing cost subject to the available testing resource. Then, a “1-dimensional integer vector coding” differential evolution algorithm with improved colony initialization strategy is proposed for the dynamic model. Comparison results with existing models show that the proposed approach is effective and efficient for solving the testing resource allocation problem, therefore providing a way to reduce the consumption of the testing resource and to improve the reliability and development efficiency of series-parallel software systems.