This paper intended how to reduce the problem of control valves. The control valve is an important component of the total process control loop, and proper valve sizing is essential for this final control element to fulfil its role. The correct process data and accurate knowledge of maximum and minimum flow conditions can reduce the problems of control valve. Selection of correct valve sizing, flow phenomena of fluid like laminar flow, turbulent flow, Newtonian & non Newtonian fluid etc. are the problem reduction points. The study of control valve sizing is based on the science of fluid dynamics. The information in this paper is an overview of current knowledge, which is continually growing.