A new method for the highly selective determination of citrulline in the melon pulp was established by capillary electrophoresis coupled with electrogenerated chemiluminescence detection （CE-ECL）,based on the N methylation derivatization reaction of the α-amino groups in citrulline molecules,with formaldehyde and sodium borohydride as main derivatization reagents to obtain a single derivative product emitting a strong electrochemiluminescence signal.Under the optimized experimental conditions,the citrulline derivative could be separated within 5 min,and there existed a good linear relationship（r2=0.999 6）between the electrophoretic peak intensity of the derivative and the original concentration of citrulline in range of 9.0-250 μmol/L with the detection limits of 3.2 μmol/L（S/N=3）.The relative standard deviations of peak height and migration time for the same standard sample（n=6）were 2.6% and 0.92%,respectively.Additionally,four kinds of actual melon samples were quantitatively determined by the standard addition method.Results showed that the citrulline contents in fresh melon pulp tissues of watermelon,melon,seeding melon and cantaloupe melon were 2.75,0.95,1.26 and 1.19 mg/g,respectively,while the recoveries for these real samples were between 91.4% and 106%.