In the past few years, robots have become an important means of substation inspection, and robotic inspection technology for non-fixed lines has received increasing attention in order to perform inspection tasks more flexibly. How to achieve high-precision positioning in complex substation environments is one of the core problems to be solved. It is difficult for a single sensor to meet the requirements of reliable positioning in substations, therefore, this paper designs a multi-sensor fusion LINS-GNSS positioning method. Its front-end tightly couples LiDAR and inertial navigation based on an iterative error-state Kalman filter framework, which recursively corrects the estimated state by generating new feature correspondences in each iteration. The back-end uses a factor graph optimization approach to loosely couple the localization results from the satellite navigation with the localization results output from the LiDAR-SLAM back-end. The optimization process first aligns the local coordinate system with the global coordinate system, then adds the position constraints of the GNSS as a priori edge to the factor graph in the back-end, and finally outputs the positioning results in the global coordinate system. In order to evaluate the performance of the LINS-GNSS system in the substation environment, this paper conducted field tests of real scenarios. The experimental results show that the LINS-GNSS system can achieve a positioning accuracy better than 1m in the substation environment.