Abstract: Experimental observation and measurement were performed for the horseshoff ortex in turbulent boundary layer through using a new method of visualization-moving sheet of laser light and several experimental skills. It was discovered and described that the horseshoe vortices form in four ways: secondary instability, combination, deformation and burst. The formation and development of these horseshoe vortices were studied and compared. The test results show that these horseshoe vortices are different in size, ...