Gap is a common disturbance regime in forest ecosystem.This paper studied their forming characteristics in an evergreen broad-leaved forest in Tiantong National Forest Park, Zhejiang Province.The results showed: the linear gap density in the forest is 17.08 gaps/km, the expanded gaps occupy 15.42％, and canopy gaps occupy 5.46％.The yearly gap forming frequency is 0.287％ and the forming rotation is about 348.4 a.The gap size is smaller than other regions, its expanded gaps vary from 39.3 m2 to 251.2 m2 and the average size is 106.32 m2.Canopy gaps vary from 11.8 m2 to 131.9 m2 and the average size is 37.68 m2.Standing litter, wind damage and selective lumber are main manners of gaps formation, most of gap-makers are Schima superba, Pinus massoniana, Castanopsis fargesii, Lithocarpus glaber, Lithocarpus harlandii,and so on.They are all dominant species in tree layer in this region.The types of gap-makers are different at different landforms.The average gap-maker number in each gap is 1.76, the main distribution range of Base Diameter（BD）of gap-makers is from 20 cm to 40 cm,and their average BD is 28.93 cm.