A functional flip cover protective case having a physical keypad and a transparent viewing window for touch-based smart phone device is being disclosed. The functional flip cover protective case comprising an integral flip cover attached a protective case; the flip cover includes a built in physical keypad device and a transparent viewing window on the front side of the flip cover when the flip cover is in closed position; wherein the flip cover further comprising a sensor to detect opening and closing actions; wherein the protective case may comprising a data/power connector, and/or a Bluetooth device, and/or a NFC (Near Field Communication) device for corresponding between the physical keypad and the smart phone device; wherein upon closing the flip cover, the physical keypad will be activated to take over the input controls of the smart phone device. In addition, the display output on touch screen of the smart phone device will be limited within the boundary of the transparent viewing window; wherein upon the opening the flip cover, the physical keypad will be deactivated and return the input controls to the smart phone device; wherein further comprising a software module to be installed in the smart phone device to correspondence with the censor and physical keypad of the flip cover.