This paper presents our design concept of a new rotor blade for an existing 300 kW WTGS with a horizontal axis rotor. This two-bladed WTGS is evaluated to have rather poor performance in terms of annual output due to the deficiencies in aerodynamic design of blade and its high noise emission level which restricts the time range of operation. The new blade must be adaptive to the existing hardware, e.g. the flange for installation and the hub and tower to assure a clearance in case of blade feathering. In order to reduce noise, and at same time, achieve high performance at the given tip speed ratio, a narrow design path was found which gives compromise among the conflicting requirements. This paper presents the outcome of this design with the airfoil, plan form and twist distribution which can attain the Betz limit on the blade from 30% to 95% radial position at the design tip speed ratio of 7.0.