Since the 18th Congress,the CPC Central Committee with Comrade Xi Jinping as its core has adhered to start the work with investigation,taking investigation as the"basicskill"for finishing all the work well,and made a comprehensive and systematic e-laboration of the investigation issues,thus forming the discourses on investigation with rich connotation,profound discussions and pre-cise logic.The formation of Xi's important discourses on investigation has profound theoretical,historical and realistic basis.These discourses'main content and core principles systematically expound the significance,scientific connotation,general requirements,methods and steps,and requirements of the investigation.Especially,overcoming new contradictions and problems,dealing with new tests and new dangers,and carrying out the new targets and new tasks constitute their spiritual kernel and essence.Xi's important dis-courses on investigation not only provide fundamental guidance for the whole Party to promote investigation,but give important methods for solving the unique problems of the major Party.It is a behavioral guide for improving the ability of investigation,and is also a sci-entific guide to purifying the political ecological environment.