The method for calculating the eco-environmental water requirement in the Zhalong Wetland are studied,and the methods for calculating the appropriate quantity of the eco-environmental water requirement and calculating the minimum quantity of the eco-environmental water requirement are put forward. The eco-environmental water requirement in all kinds of the land use area in the Zhalong wetland including the lake, in the swampland saturating with water and in the swampland covering with bulrush, the appropriate quantity of the eco-environmental water requirement and the minimum quantity of the eco-environmental water requirement are calculated and analyzed. It is concluded that, the quantity of the eco-environmental water requirement in the whole Zhalong Wetland varies from 522 millions m³。592 millions m³ during from 1986 to 2002, the appropriate quantity of the eco-environmental water requirement is 555 millions m³, the minimum quantity of the eco-environmental water requirement with the ascuring probability of 75% is 289 millions m³ and the minimum quantity of the eco-environmental water requirement with the assuring probability of 95% is 354 millions m³.