Scanning electron microscope, differential thermal analysis, thermo-gravimetric analysis,fluorescent analysis and X-ray CT et.al.have become usual means used in the research of concrete material science.This paper proposed a new method to evaluate the causes of cracking of in-situ concrete based on the investigation by using these comprehensive technologies for analysis of micro-structure.The proposed new method is more reliable and objective than the traditional method which is mainly based on experience and chemical analysis.A case investigation using the new method to explore the causes of cracking in a real project was introduced.