In order to solve the problem that a large number of detail features are missing after the simplified three-dimensional grid model of transmission towers, a lightweight algorithm for the three-dimensional grid model of transmission towers is proposed based on Quadric Error Metrics algorithm. The algorithm firstly defines the detail features in the 3D grid model of the transmission tower, then proposes the detail feature extraction strategy of the transmission tower, and introduces the detail feature significance factor and vertex approximate curvature factor to optimize the folding cost in the QEM algorithm. The experimental results show that the improved algorithm can effectively retain the important geometric features and detailed features of the three-dimensional grid model of the transmission tower, avoiding the problem of large-area feature loss in the simplified model, and compared with the ordinary QEM algorithm, the maximum error, mean error and mean square error of the simplified model are reduced by at least 39.77%, 10.64% and 64.99% respectively, which realizes the high quality and lightweight of the three-dimensional grid model of the transmission tower.