??For improving soil depth accuracy of river crossing section signal value is got by cable or ground loop method in the river crossing section. It takes one or more calibration points to correct signal value. Soil depth of underwater crossing sections is calculated by Ariver .It achieves good effect. The results show that: cable loop method and taking a calibration point on both sides of the river are more high accuracy than others. Error is within the allowable range. The work meets practical requirements of underwater inspection.