Based on four seasonal oceanographic survey data during 1997- 2000 in the East China Sea ( 23o30c~ 33oN, 118o30c~ 128o00cE) , eco logical characteristics such as quantity, community characteristics, species composition and dominant species were approached. This paper is first part; it shows that pelagic copepods abundance occupies about 55. 5% of total abundance in the East China Sea and about 64. 8% diet total abundance. Abundance peak occurred in autumn. Second peak occurred in summer, and the lowest abundance appeared in spring. It s horizontal distribution was not even. Normally, it s abundance in coastal water is higher than that in off sea and Taiwan Strait, high abundance region appeared in convergence region of waters. Among them, its abundance value of convergence region of coastal current water and of f seawater was higher than that in other mix region. Its abundance value of copepods was about 1/ 3 value only compared with 20 years before in the north part of the East China Sea( 29b~ 32bN、west of 125bE) . Horizontals distribution of pelagic copepods in the East China Sea is dependent upon some dominant species such as Calanus sinicus , Euchaeta concina, Eucalanus subcrassus etc.