The invention discloses a voltage phase-lack algorithm in a measurement abnormality analysis system. Through a mathematical statistic analysis mode, a data model achieves high automatic judgment on a result, the smoothness of time is achieved, through theoretical analysis and practice verification, precise event judgment can be achieved, the workload of manually carrying out data judgment and statistic analysis is reduced to a large extent, work efficiency is improved, the analysis base of data is achieved, and the timeliness and the accuracy of phase-lack event judgment are effectively guaranteed. Based on an on-line measurement abnormality monitor system, auxiliary information is provided for the safe, reliable and economic operation of a distributed power grid, and therefore guidance is provided for the power supply service with higher reliability.