After the induction of triploidy in carp (Cyprinus carpio) by cold shock, chemical shock, or hydrostatic shock, the identification of triploidy presence using flow cytometer to determine DNA content was developed and compared with three other methods, including karyotyping method, silver staining method and Coulter counter method, which were previously used in our laboratory. Three major protocols A, B and C adopted for pretreatment of red blood cells were found to be feasible and pratical with stepwise improvement of easy manipulation. The treated RBC samples were run in a flow cytometer allowing the sample injection at optimum flow rate (15～30 *l/min) sheath pressure (7.51～15.00 PSI) and laser power (0.15 MV and 8.62 A) to obtain better half pick coefficient of variation (< 5%) and histograms of fluorescence intensity from RBC stained with PI (Propidium Iodide). The histograms were analyzed using the supplied DNA analysis program and a recommended software. The results indicated that the flow cytometer has the advantages of being accurate and capable of checking more than 10,000 cells within 3 min. In this study, cold shock of 1℃ resulted in triploidy of 66.6, 80.4, 86.2 and 86.4% in various experimental groups, while high Ca, high pH solution treatment and hydrostatic pressure shock gave poor production of triploidy.