The tooth profile serves as a crucial geometric information carrier for characterizing gear errors. Comprehensive tooth profile information is essential for process error analysis, quality evaluation, and proper gear meshing. This paper proposes a method for measuring and evaluating complete tooth profile information based on line structured light. Firstly, a full-information measurement model of the tooth profile is developed using a line structured light (LSL) sensor, enabling rapid and precise data acquisition from both sides of the gear. Secondly, leveraging the capabilities of large optical measurement sample sizes and comprehensive data, a new method for characterizing profile deviation is introduced, consistent with the ISO 1328 gear standard. This method allows for uniform characterization and statistical evaluation within the O-FTB framework. Experimental analysis confirms that the measurement system’s accuracy is comparable to that of a gear measurement center (GMC), with a discrepancy of less than 5.4 µm. Nine repeated experiments were conducted. The full-information error characterization visually illustrates the holistic deviation distribution of the gear, providing a foundational basis for error source analysis. Statistical results demonstrate that the proposed evaluation method effectively characterizes the holistic quality of the gear.