WiFi-based indoor positioning is widely studied due to its cost-effectiveness and broad coverage. This research focuses on Time-of-Flight (ToF) positioning using Channel State Information (CSI) to enhance accuracy. We first explore the relationship between ToF and CSI in a single-path scenario. We then use triangulation and the MUSIC algorithm to determine the transmitter’s position. Real-world data analysis addresses both linear and nonlinear errors, and a two-step method of data cleaning and optimization based on simulated annealing algorithm is introduced. Our approach outperforms traditional methods like L-BFGS, providing a more accurate indoor positioning solution and a quantitative error estimation.