In order to measure the graininess of metallic paints, a measuring device and evaluation method were developed, the evaluation model of metallic paint graininess effect applied to the measuring device was established. According to different color distributions and particle sizes, 56 metallic paints were selected to construct the sample database. The particle parameters of samples were collected by BYKMac, and visual experiments were performed to verify the accuracy of BYKMac data. The measuring device was designed to obtain sample image information, the existing texture evaluation methods were used to process the image information and the data is compared with the visual experiment data. At the same time, an evaluation method suitable for the device was designed to get the graininess value of the samples. The correlation coefficients between the measurement results and the visual values and BYKMac values were 0.8770 and 0.9329, respectively. Experimental results show that the measuring device and evaluation method can effectively measure and obtain the graininess of metallic paints that meet the perception of human eyes.