Soil salinization is serious in Xinjiang, and it is urgent to prevent the spread of soil salinization. Water and salt contents can directly indicate the degree of salinization, so their rapid inversion is of great significance for preventing soil salinization. In this paper, typical cotton fields with drip irrigation under mulch were selected in Xinjiang, wave velocities were obtained with 250 MHz and 1 000 MHz antennas of ground penetrating radar (GPR) through common center point method and were converted to apparent dielectric constants. Meanwhile, combined with field measured data, the parameters in Hu Qingrong dielectric model of saline soil were modified, water and salt contents in topsoils (0-30 cm) of selected cotton fields were inversed by the modified model, and the inversion results were also verified. The results showed that the corrected value was 0.74 for parameter A and 0.14 for parameter ξ in Hu Qingrong dielectric model, and the modified model was feasible for the inversion of soil water and salt contents in cotton fields with drip irrigation under film. Water content inversed better by 1 000 MHz frequency antenna than by 250 MHz frequency, and inversed value had significant linear correlation with measured one (R²=0.948, RMSE=2.67 cm³/cm³). Salt content in topsoil of cotton field could be effectively inversed by combining 250 MHz and 1 000 MHz frequency antennas of GPR, and inversed value fitted well with measured one (R²=0.835, RMSE=1.43 g/kg). In conclusion, the modified model combined with GPR could not only improve the survey efficiency of water and salt contents in cotton fields, but also helped edit the distribution map of soil water and salt contents in cotton fields at meso-scale, which provided theoretical data support for soil salinization prevention.