Abstract: An improved penile electroejaculation using absorbent cotton and aluminum as electrodes to avoid the small superficial burns or more serious lesions was employed on the Rhesus monkey (Macaca mulatta),Tibetan macaque (M.thibetana) and Assamese macaque (M.assamensis) and the semen parameters of the animals was compared in the present study.The pattern of stimulation for ejaculation was stepwise and consecutive increasing of voltage.No penile burns or lesions resulted from the electroejaculation procedures.It was effective to use the pattern of stepwise stimulation for the animals at the first on the penile elctroejaculation.Semen parameters of ejaculates obtained by the method from rhesus,Tibetan and Assamese macaques were as follows,semen volume(ml):2.0±0.1,6.3±1.1 and 3.2±0.6;liquefaction(ml):0.7±0.6,2.1±0.4 and 1.7±0.3;concentration (×108／ml):12.6±1.2,45.6±5.6 and 11.5±0.9;coagulum liquefaction rate (%):36.2±0.9,34.0±1.4 and 51.8±1.2,respectively.No correlation was established between the sperm number and the amount of coagulum or the volume of semen (r2=0.079;0.016;0.094;and r2=0.064;0.020;0.072,respectively) in the three species.These results indicate that:1) the improved penile electroejaculation is suited to rhesus monkey,especially to Tibetan and Assamese macaques with the rough penile surface;2) The semen volume and sperm number of the Tibetan macaque are the largest in the nonhuman primates compared with the previous reports.Its semen may be a good materials for study on spermatology.