In the field of construction machinery, different shapes of the noncircular opening throttling grooves are often taken in multiway valve for different flow control characteristics. Because of the complex and changeable structure characteristics of noncircular throttling grooves, the traditional and relatively simple calculation formula of the crosssectional area is difficult to complete the accurate calculation of the area. CFD simulation software was used to simulate and analyze the threedimensional flow field pressure of dualU throttling groove,and the relationship between the area and the pressure was deduced. The local pressurelosscoefficient according to the liquid flow form was determined,and the relationship equation between the calculation area of noncircular opening and the structure parameters of the throttling groove was obtained. AMESim simulation and test results are basically the same. The results indicate that this method can quickly and accurately complete the design of opening area about various noncircular opening valve,which has important significance for flow designing, flow force prediction and the control of vibration and noise.