In order to accurately evaluate the thixotropy of Zhanjiang Formation clay, based on the fuzzy mathematics theory and according to the influencing factors of clay thixotropy, a fuzzy comprehensive evaluation factor set of clay thixotropy strength was constructed with clay content, pore ratio, plasticity index and sensitivity as indicators. A comprehensive evaluation set of clay thixotropy strength and the grade standard of thixotropy strength evaluation index were established. The membership degree and weight of each index were calculated by using the fuzzy comprehensive evaluation method, and the classification standard for the strength of thixotropy of clay was established. The thixotropy strength of structural clay of Zhanjiang Formation was graded by using this standard. The results show that strong structural clay of Zhanjiang Formation under each sedimentary facies has strong thixotropy, and the thixotropic strength from strong to weak is in the order of Leinan fluvial facies, neritic facies, estuarine facies and Leibei fluvial facies.