Objective To explore the influence factors and experimental conditions of phototoxicity test using pure UVA light source.Method The variations of light intensity associated with the exposure duration,the influence of exposure duration to UVA radiation on the temperature of the exposed area were both observed.The phototoxicity of positive control of 8_methoxypsoralen(8_MOP)to skin of healthy adult guinea pigs exposed to UVA radiation at dose of 10 J/cm2 for about 50min was observed also.Results The intensities of UVA light source were stable in the range of 3.3～3.4 mW/cm2 during the period of 100 minute_radiation.After a 100 minute_exposure to UVA radiation at 18 ℃,the temperature of the irridiated area increased 1.5 ℃,8_MOP revealed significant phototoxicity.Conclusion This method for phototoxicity test using pure UVA light source could examine the phototoxicity of a certain chemicals accurately,which was scientific and feasible.