The invention discloses a method for optimizing a unit regression test case set based on a control flow diagram. The method comprises the following steps: A, finding out modified points corresponding to a modified part from the control flow diagram of a tested unit being tested unit before and after; B, screening out test cases, of which the execution paths pass through the modified points, to serve as one part of the regression test case set, namely a selected test case set (Tselected), and running all the test cases in the set; C, calculating all the reachable successor nodes of the modified points and selecting a node subset N which is not covered in the running process of the step B; D, if the N is null, executing the step F, and if the N is not null, executing the step E; E, selecting one node from the N to serve as a coverage target generation test case, adding the coverage target generation test case into a new test case set (Tnew) and then completely running, updating the N, deleting the nodes covered in the running process and returning to the step D; and F, finishing construction of the regression test case set (TR). By application of the method, the efficiency of the regression test can be improved and the effectiveness and the sufficiency of the regression test are guaranteed.