The invention discloses a multifunctional breather valve. The multifunctional breather valve includes a breather valve body, a pipe, and a patient end interface, a spray gas connection port and an exhaust port arranged in the pipe. A one-directional inhalation valve is arranged in the gas-spray gas connection port. A limit board is arranged in the exhaust port. The limit board is provided with a communication port. An expiration resistance adjusting device is arranged for the communication port. The expiration resistance adjusting device includes a one-direction expiration valve, a reset spring and a resistance adjusting device. According to the invention, spray gas can be inhaled into the lung part fully and is output during the inspiration process synchronously, secreta is discharged timely, the pipe pressure is stable under different pressure levels due to noninvasive mechanical ventilation and lung injury caused by over high airway pressure during the mechanical ventilation process is avoided. The multifunctional breather valve is suitable for serving as a one-direction valve for aerosol inhalation treatment, an exhalation valve for shock sputum excretion and noninvasive mechanical ventilation, a cough pressure relief valve during the mechanical ventilation process and a valve for breath muscle exercise.