Abstract: In this paper, the characteristics of sporadic E layer (Es) is discussed, using data measured from China vertical stations of Haikou (20.02°N, 110.20°E), Lhasa (29.39°N, 91.08°E) and Changchun (43.54°N, 125.19°E) for one solar period between January 1976 and December 1986. The diurnal, seasonal and solar activity variations of Es occurrence probability with critical frequencies greater than several special values (f₀E_s > 3, 5, 7, 9MHz) are discussed. The obscure property is also analyzed. The results show that: the most significant occurrence probability presented during daytime in summer months, and does not depend significantly on solar activity. The distribution regularity is of great difference with different stations, and in most cases, Lhasa has the biggest occurrence probability. As to the blanketing property, three stations also have different distribution characteristics, except for that the obscure probability in summer is bigger than other seasons and is bigger in solar minimum than solar maximum too.