A robust passive high frequency high pressure micro check valve was developed for piezoelectrically actuated pumps. A novel cross-patterned microvalve flap is used to increase the valve’s structural stiffness with pressures up to 10MPa. A mechanical valve stopper prevents valve-flap failure under extreme high pressure. The valve-flap is also designed to work at frequency larger than 10,000Hz. The valve-flap was fabricated with electroformed nickel on silicon substrate. Deep RIE etching was used to fabricate the valve channels in the silicon substrate. The whole valve weighs 0.2g including packaging. The microvalve flow rate (water) is measured to be 18cm 3 /s under a pressure difference of 50psi. The microvalve was integrated with a compact piezoelectric pump and produced pressure of 350psi when operated at 10kHz frequency.