An effective in-situ monitoring method for MPCP is urgently needed in civil engineering field. In this research, a quick and accurate in-situ measuring method for mix proportion of concrete is put forward. This method can succeed in measuring real mix proportion of any concrete paste precisely within 20 minutes according to four parameters of concrete before initial setting time of concrete. By comparing the designed mix proportion of concrete with the real measured one in construction site by this method, the quality of concrete can be demonstrated. This method can evaluate the reliability of mix proportion for real concrete in construction site quickly and precisely, and ensure the quality of concrete structures to avoid the occurrence of engineering accidents.