Using the innovation evaluation theory, a comprehensive evaluation of the technological innovation capability of China's petrochemical enterprises was given. During the evaluation process, the assessment model did not fit the particular type of business, resulting in issues such as inaccurate evaluation results and many subjective factors in the evaluation. According to the views of other scholars, a set of evaluation index system for technological innovation capability of the petrochemical industry was created. By combining AHP and GRAP, a multilevel gray comprehensive evaluation model was established. According to the analysis, the economic indicators of four enterprises were obtained, and these four companies were evaluated by using the assessment model. Finally, according to the evaluation results, suggestions on how to arrange funding of innovative projects and how to enhance the technological innovation capability were provided.