A mica water level gauge glass includes a steam tee fitting, a balance pipe, a water tee fitting, a steam connecting pipe, a water connecting pipe, a condensation tank, a longitudinal vertical gauge body, and a mica assembly. The gauge body includes a thermal compensation cavity, a steam-water cavity, an auxiliary heat confluence device, and a horizontal steam cavity. The exit points of the thermal compensation cavity arranged in the gauge body is lower than the point of the steam-water cavity exiting from the gauge body.