Abstract: As the requirements for precision measurement and precision machining continue to increase, the measurement of the thermal expansion coefficient (CTE) of materials has become more and more popular, and the uncertainty evaluation of the measurement results is becoming more and more important when using commercial CTE measurement equipment for metrological traceability. The maximum permissible error, the accuracy of the length measurement of the instrument, the accuracy of the constant temperature of the furnace, the accuracy of the temperature measurement of the instrument, and the repeatability of the measurement results will all directly affect the uncertainty evaluation of the measurement results. In this paper, the uncertainty of the measurement results of the thermal dilatometer is evaluated according to the GUM method. While analyzing the error source of the thermal dilatometer of the laser absolute method, a complete measurement model is given, and the synthetic uncertainty of measuring standard quartz samples is calculated according to the model. The user can assess the uncertainty of the measurement results of the self-use equipment according to the error analysis of the laser absolute method of measuring the CTE.