The invention provides a three-dimensional scanning system for appearance detection of a low-voltage current transformer. The three-dimensional scanning system comprises a low-voltage current transformer installation module used for installing the low-voltage current transformer to be tested and controlling the translation and rotation of the low-voltage current transformer to be tested, a grating transmitting module used for projecting the grating to the low-voltage current transformer to be tested, an image acquisition module used for acquiring the image of the the low-voltage current transformer to be tested after grating processing and sending the image information to a data processing module and the data processing module used for analyzing the image information sent by the image acquisition module and comparing the analyzed image information with a three-dimensional image information of the standard low-voltage current transformer to calculate the detection error of the low-voltage current transformer to be tested. According to the technical scheme of the three-dimensional scanning system for appearance detection of the low-voltage current transformer, an automatic and accurate measurement of the appearance dimension and the error of the low-voltage current transformer to be tested is realized, the measurement result is more accurate and reliable, and the measurement process is faster.