The invention relates to the technical field of mechanical experimental devices and testing methods, aims to solve the problems that the test device for crack fatigue propagation rate in the prior artcannot conveniently realize the alignment of samples, and the test precision and reliability are insufficient, and provides a test device and a test method for I-II composite crack fatigue propagation rate. The test device for I-II composite crack fatigue propagation rate comprises two clamps for respectively clamping both ends of a sample, wherein each clamp comprises two clamp plates having opposite surfaces and a locking structure connecting the two clamp plates; the locking structure is configured to lock the two clamp plates to clamp the sample or to loosen the two clamp plates to release the sample; and the clamps are configured to be clamped on the corresponding end of the sample in the form of making the corresponding end of the sample clamped between the two clamp plates and connected onto the locking structure. The test device and test method for I-II composite crack fatigue propagation rate provided by the invention have the beneficial effect of conveniently ensuring that the clamped sample is in the correct, for example, centered posture, thereby ensuring the accuracy and reliability of the implementation.