Hepatic cells apoptosis induced by olaquindox in common carp, Cyprinus carpio , were studied. The test was conducted for 30 days, with dose of 200mg..kg - 1 feed. Terminal deoxynucleotidy transferase mediated dUTP-Biotin nick-end labeling ( TUNEL) , electronic microscopic and flow cytometry were performed to analyze apoptosis. The result showed that hepatic cells apoptosis were indent ified under light microscope with TUNEL staining; chromatin condensation, chromosal clumping and margination, and apoptotic bodies were observed under electronic microscope; and sub-G1 PEAK ( AP peak) in hepatic cells could be detected by f low cytometric method. The apoptotic rate measured by flow cytomtry increased with dye-poison time, on the 7th, 14th, 20th, 25th and 30th day, the apoptotic rate was 2. 05%, 6. 25%, 9. 49%, 13. 31% and 17. 44% respectively.