Abstract: Based on the method of evaluation and expression of the uncertainty of measurement, a mathematical model to determine the uncertainty of the measurement of formaldehyde content in non metallic materials in a vehicle is established using high performance liquid chromatography(HPLC), and the sources of each uncertainty component in the test process are analyzed and synthesized. The results show that the fitting of the standard curve and the repeatability of the experiment have great influence on the experimental results. Through standardizing the operation of the preparation of standard solution, and reducing the uncertainty of measurement results, the accuracy and consistency of detection can be improved.