Abstract: Electromagnetic wave CT is widely used in the detection of carbonate karst cave, but it is often affected by the geological conditions of the work area and the site construction conditions, causing anomalous artifacts that are difficult to explain. The forward model is applied to the processing and interpretation of the rock mass under the main bearing platform of Chishui River Bridge through the discussion and the establishment of the forward model. The effect of the pile foundation abnormal body on the measurement results is solved. Combining with the characteristics of construction site, the detection results are divided into surface effect anomaly area, well wall response anomaly area, pile foundation and surrounding rock comprehensive response anomaly area, complete surrounding rock area, and good application effect has been obtained.