Abstract: In order to effectively deal with the reconnaissance threat of modern radar to air defense targets and improve the ability of camouflage protection, this paper takes the civil air defense engineering cave as the research object, and uses the methods of simulation and scaling model measurement to compare and analyze the characteristics of radar echo. By acquiring the echo thermal maps of targets in different threat directions and construction conditions, combining with the detection probability, the exposure symptoms in echo contrast and orientation are confirmed. On this basis, an engineering application method combining random undulating profiled thin shells with absorbing coatings is proposed. The test results show that the method is effective in improving the echo characteristics, and it is manifested in reducing echo contrast and makes the echoes in all directions more uniform at the same time. Meanwhile, it is effective to counter the threaten of radar wave from multi-angle incidence, thus it can provid technical support for camouflage design.