Objective: To investigate the effect of C-phycocyanin (C-PC) on the epithelial-mesenchymal transition (EMT) of cervical cancer Caski cells induced by transforming growth factor beta1 (TGF-β1). Methods: According to different treatment methods, Caski cells were divided into three groups: 10 ng/ml TGF-β1 treatment group, 10 ng/ml TGF-β1+300 μg/ml C-PC co-treatment group and control group (untreated). After 24 h of treatment, the morphological changes of Caski cells were observed, and the effects of TGF-β1 and C-PC on the migration and invasion of Caski cells were detected by Scratch test and Transwell test, respectively. Western blotting was used to detect the effect of C-PC on the expression of epithelial phenotypic marker protein E-cadherin and stromal phenotypic marker protein N-cadherin in TGF-β1-induced Caski cells, and qPCR was used to detect the mRNA expressions of EMT related factors Snail, Zeb1 and Twist. Results: Caski cells in the TGF-β1 treatment group lost the characteristics of the original epithelial phenotype, while the cells in the TGF-β1+C-PC co-treatment group maintained the characteristics of normal epithelial phenotype; the migration rate ([60.0±1.4]% vs [33.5±2.2]%, [40.0±2.8]%, both P<0.05) and the number of invasive transmembrane cells ([108.2±6.2] vs [25.2±3.1], [39.8±5.4], both P<0.01]) of Caski cells in the TGF- β1 treatment group were significantly higher than those in the co-treatment group and the control group. Compared with the control group, the expression of E-cadherin in Caski cells treated with TGF-β1 decreased significantly (P<0.05), while the mRNA expressions of Twist, Snail and Zeb1 increased significantly (all P<0.05); However, co-treatment with C-PC reversed above changes (P<0.05 or P<0.01), and significantly decreased the protein expression level of N-cadherin (P< 0.05). Conclusion: C-PC treatment can inhibit the invasion and metastasis ability of Caski cells induced by TGF-β1 and further affects the EMT process. The mechanism may be related to the decrease of mRNAexpressions of Twist, Snail and Zeb1 by C-PC treatment. ·