To explore the biological functions of polyamines, the analytical method of polyamines by capillary electrophoresis with laser-induced fluorescence detector (LIF) was developed. After derivatization of polyamines with isothiocyanatefluorescin, using borate (pH 8.6) as running buffer, putrescine, spermine, spermidine and 1,6-diaminohexane were separated successfully within 8 min at the voltage of 20 kV. The linear range, stability, detection limit and recovery were examined, the method was simple, sensitive and rapid. The results of polyamines in serum showed: The levels of spermine and spermidine were significantly higher in rat serum of tumor than in rat serum of control group and non-tumor group. There was no markedly difference between the levels of spermine and spermidine in rat serum of control group and in rat serum of non-tumor group. The levels of putrescine in serum were no obviously difference between any groups.