The Prime Minister promulgated the Decision 937/QD-TTg dated 01/07/2009 that ratified the drainage plan for the Nhue river system, in which the design drainage coefficient for the inner Hanoi in the East of To Lich river is 17.9 l/s.ha. This article introduces one method in calculating the design drainage coefficient being applied for urban areas and relatively large scale centralized- industry are.as. These areas locate separately and form individual drainage regions, which directly discharge to large rivers such as the Yen So pumping station basin. The design drainage coefficient mainly depends on the characteristics of the design model of precipitation, the total natural area of each group of drainage objects, the fraction of area and flow coefficient of each group of drainage objects existing in the drainage basin as well as the period in calculating the drainage coefficient. On the ground of the calculating results, this paper presents some comments about the suitability of the design coefficient, which is approved as above, proposes the selection of drainage coefficient in designing calculation and construction of local drainage works to convey water from metropolitan area or from sub-basin into the common drainage network of the city so as to transfer to Yen So pumping station.