The paper discussed the requirement and significance of engineering investigation for the application of trenchless technology in the diversion of rain and sewage of urban drainage system. According to the analysis on comparison between specification of trenchless technology and routine municipal engineering investigation, engineering investigation characteristics of trenchless technology construction was learned. With the trial section project of the diversion of rain and sewage drainage system of Langfang city, analysis was made on the influence of earlier investigation upon late trenchless construction, and the importance to trenchless engineering design and construction by engineering geological investigation and underground pipe detection was clarified. In the end, the paper summed up the routine work of engineering investigation for trenchless technology construction to give the reference in the diversion of rain and sewage to more urban drainage systems.