The existing support directional valve can only complete the switch control function of “On/Off” of support fluid supply. In order to solve the problem of severe pressure impact in the support hydraulic system caused by this, an improved design scheme of the directional valve with triangular non-circumferential opening throttling groove in the main spool was proposed.The calculation formula of the throttling area of the triangular valve orifice was obtained.A hydraulic directional valve model of the main spool with triangular groove was built based on AMESim,and a comparative study on the performance of the original valve and the improved valve was conducted.The results show that after the addition of a triangular throttling groove in the main spool, the variational gradient of the flow area of the valve orifice is segmented to increase, that is, when the spool opening is less than 8 mm, the average gradient of the flow area of the valve orifice is 5.5 mm2/mm; when the spool opening is more than 8 mm, the gradient increases to 92 mm2/mm; the flow rate though the valve orifice and the working pressure at the valve orifice can also achieve the graded gradient increase, so the smooth start of the hydraulic actuator can be realized and the pressure impact in the hydraulic system could be effectively alleviated. The method provides reference for the design improvement of large flow proportional directional valve of hydraulic support