A Feature-adaptive multi-scale You Only Look Once (FamsYOLO) network-based method and system for detecting surface defects of new vehicles are provided. The method includes: acquiring images of front, rear, left, right, and top surfaces of different types of new vehicles before delivery, marking vehicle surface defects in the images, and constructing an image dataset; constructing a FamsYOLO network, where a backbone part of the FamsYOLO network is serially formed by a head DBL-3 module and an intermediate residual structure from top to bottom, and a neck part of the FamsYOLO network includes, from bottom to top in sequence, a DBL-1 module, upsampling, a first feature concatenation, a FasterC3K2 module, Reshape transformation, a second feature concatenation, a FasterC3K2 module, and a Squeeze-and-Excitation Network (SENet) module; and training the FamsYOLO network using the image dataset, where the trained FamsYOLO network is used for detecting surface defects of new vehicles.