In response to the inaccuracy model of low-voltage power grid, a solution method based on AMI(advanced metering infrastructure) data and metering point errors of electricity meters is proposed. This method analyzes the energy conservation equation set of the low-voltage power grid line loss model, introduces the constrained ridge regression method into the line loss model based on the physical meaning of the line resistance coefficient, and theoretically proves that the solution of the low-voltage inaccuracy model is equivalent to an optimization problem with constrained conditions. To validate the effectiveness of the proposed method, blind tests are conducted on both laboratory simulation data and real-world data, and the results indicate that the method has a high hit rate and detection rate for small out-of-tolerance metering points, demonstrating good engineering practicality and economic value.