Every centrifugal pump has four main components, namely, casing, impeller, suction pipe and discharge pipe. The important principles and fluid mechanics theories on centrifugal pump are introduced in firstly. The detailed design procedure for volute type pump casing is carried out. In this paper, various kinds of pumps and operational sequences are described. And then, application and characteristics of centrifugal pump are also expressed. This paper relates to the design of casing of single-suction centrifugal pump that can develop a head of 30m and discharge 1.7m3/min of water at the speed of 1880 rpm. The designed impeller has 115 mm inlet diameter, 256 mm outlet diameter, 19.5? inlet vane angle and 22.5? outlet vane angle. The number of vanes is 6. The outlet width is 15mm. The discharge diameter is 3in (96mm) to operate the designed head and capacity. The maximum efficiency of the pump is 72 %. The designed single-suction centrifugal pump can fulfil the requirements of agricultural processes.