Abstract: This paper studies the comprehensive geophysical detection method and evaluation standard of karst roadbed grouting effect. The typical test areas of Nanning-Guangzhou railway karst roadbed are selected. The field test research of detection standard and characteristics are studied using resistivity method, transient surface wave method and electromagnetic wave CT method. The applicability and economy of the above geophysical detection methods are evaluated. The comprehensive geophysical detection method of variety methods combination in different engineering conditions is proposed. The differential values of resistivity, surface wave velocity and electromagnetic wave absorption coefficient are statistically analyzed using the test data of grouting. The grouting is qualified, and preliminarily obtained in the karst roadbed. The grouting effect detection standards are proposed for the above three geophysical methods. The resistivity method detection standard is that the resistivity differential values of karst cave is more than 20%, and the pebble soil is more than 10%.The transient surface wave method detection standard is that the wave velocity of clay is more than 20.6h+130.3, and the karst cave is more than 17.1h+236.9. The electromagnetic wave CT method detection standard is that the electromagnetic wave absorption coefficient differential values of karst cave is more than 0.4dB m-1, and the pebble soil is more than 0.1dB m-1.