Ventilation system and breathing machine

The ventilation system comprises a ventilation valve body, an airflow channel is arranged in the ventilation valve body, the ventilation valve body is further provided with a first air port and a second air port which are communicated with the airflow channel, and airflow can flow into the airflow channel from any one of the first air port and the second air port. And the gas flows out of the gas flow channel through another gas port. An exhaust pipe and a pressure sampling pipe are arranged on the vent valve body at intervals, both the exhaust pipe and the pressure sampling pipe communicate with the airflow channel and are located on a flowing path of airflow in the airflow channel, and the pressure sampling pipe can be externally connected with a pressure sampling device so as to detect the airflow pressure in the airflow channel. The pressure sampling pipe can be connected with a pressure sampling device, the pressure of the airflow in the airflow channel can be detected in real time, the leakage amount of