The invention relates to the technical field of buildings and civil engineering, and discloses a construction measurement system and a construction measurement method based on earth-rock excavation operation of an excavating machine. The construction measurement system comprises the excavating machine, a double-axis inclination angle sensor, an angle sensor, a range finder, a data integration module, a data computing terminal, a power supply module and the two GNSS receivers, wherein the double-axis inclination angle sensor, the angle sensor, the range finder, the data integration module, thedata computing terminal, the power supply module and the two GNSS receivers are arranged on the excavating machine; and the power supply module supplies power to the GNSS receivers, the double-axis inclination angle sensor, the angle sensor, the range finder, the data integration module and the data computing terminal. According to the construction measurement system, observation data are providedin real time while excavation construction is conducted by means of operation equipment, traditional excavation retesting and midway paying-off procedures are omitted, excavation interruption causedby retesting and paying-off is avoided, excavation continuity is improved, and excavation construction efficiency is improved; and the observation data are provided in real time during excavation construction of the excavation machine, excavation real-time monitoring is achieved, the monitoring frequency is higher than the traditional construction re-measurement frequency, the excavation precisionis improved, and over-excavation and under-excavation are avoided.