The practical problems in tracing and transferring the value of the plumb alignerare discussed in detail, including the lack of high-accuracy calibration device for the plumb aligner, the error of gravity line sensor of the plumb aligner itself, and the difficulty of ensuring the accuracy of the laser plumb aligner. The relationship between the gravity line and the plumb line is analyzed in detail, and the reasons why the plumb line is different in different geographical positions are explained. The idea to solve the problem of the traceability and transmission of the value of the plumb aligner is expounded.