The cell membrane is the protecting frontier of cells, which is crucial for maintaining cell integrity, and has a close relationship with cell growth and death. There is a growing need for cell membrane imaging and monitoring in both living and dying cells. Herein, we report a new amphiphilic tetraphenylethene-based pyridinium salt (TPE-MEM) with aggregation-induced emission features for discriminatory cell membrane imaging. The fluorogenic probe with high yield was synthesized following asymmetric McMurry reaction, Williamson ether synthesis reaction, Suzuki coupling, and aldol condensation between a double-charged pyridinium salt and hexyloxytetraphenylethene benzaldehyde. TPE-MEM shows good water solubility, biocompatibility, and cell membrane specificity. Interestingly, a reactive oxygen species (ROS) is produced by the molecule (TPE-MEM) under room-light irradiation, which could destroy the integrity of the plasma membrane and cause cell necrosis. This enables a visible observation of cell necrosis and the phototherapeutic effect under a mild condition. Preliminary animal investigations also demonstrated the photodynamic therapy (PDT) effectiveness of TPE-MEM in tumor growth inhibition. We conclude that TPE-MEM is potentially a cell membrane-selective photosensitizer for PDT and it is worthy of further exploration of the phototherapeutic effect on animals systematically.