The invention discloses a non-invasive ventilator capable of reversely adjusting inhaling/ exhaling pressure ratio. The non-invasive ventilator comprises a mask, and a turbine motor which is communicated with the mask through an air pipeline; a solenoid valve is arranged on the air pipeline and used for regulating the output pressure and flowing velocity of the ventilator and lowering down the minimum IPAP or EPAP pressure to be zero. According to the non-invasive ventilator, the solenoid valve is arranged and can quickly switch inhaling pressure and exhaling pressure, thus the problem that the inhaling pressure cannot be less than the exhaling pressure can be solved, and an optimal optional scheme is provided for the early treatment of sleep apnea hpoventilation syndrome and chronic obstructive pulmonary disease.