Abstract: To improve the unsteady wind tunnel test technique on multi-bodies separation, and make the relevant researcher further understand the technique, the characteristics, similarity criteria, and application field are summarized for two unsteady wind tunnel test techniques on multi-bodies separation, which are multi-bodies separation wind tunnel free-flight test and wind tunnel drop-model test techniques. The difference between two techniques is analyzed. Comparison is made between heavy scaling and light scaling, for both wind tunnel drop-model test and multi-bodies separation wind tunnel free-flight test technique. The applicability is analyzed for the two unsteady multi-bodies separation wind tunnel free-flight test techniques, on various multi-bodies separation, such as stage separation, submunition disperse, cover separation, weights disperse, shroud separation, jettisons of airborne external stores and internal missile separation.