Abstract: Objective To study the difference in ultraviolet(UV) exposures on horizontal and vertical plane,and to analyze the effect of snow reflect on UV exposures on both planes.Methods The UV exposure values on the horizontal and vertical plane were measured in winter(before and after snowing) and summer days using solar-UV sensors in Shenyang,China(41?51'N,123?27'E).Results The horizontal UV exposure distribution showed bell-shaped curves in winter(both before and after snowing) as well as in summer,which was consistent with the results of previous studies.The cumulative dosage of a half hour reached the peak value at midday(15 kJ/m² before snowing in winter,17 kJ/m² after snowing in winter and 93 kJ/m² in summer.Vertical UV exposure distribution also showed bell-shaped single peak curves in winter(both before and after snowing).However,the distribution in summer was significantly different,showing bimodal curves with the peak values of a half-hour cumulative dose at 7:30-8:00(11kJ/m²) in the morning and 15:00-15:30(12 kJ/m²) in the afternoon.On the first day after snowing,the UV was reflected strongly from the snow surface.The horizontal UV exposure slightly higher than that before snowing(an increase of approximately 13.9%),while the vertical UV exposure significantly higher than that before snowing(an increase of about 98%),and even higher than that in summer(an increase of about 61.7%).Conclusion At morning and evening time in summer and the time after snowing in winter,the protection of some human anatomic sites that approximate vertical plane,especially the eye,should not be ignored.