The invention relates to an engine gas distribution mechanism, an engine and a vehicle. The engine gas distribution mechanism comprises a cam shaft and a rocker arm assembly. The rocker arm assembly comprises an exhaust rocker arm and a waste gas rocker arm. The cam shaft comprises an inner shaft and an outer shaft. A waste gas cam is fixed to the outer shaft. An exhaust cam is fixed to the innershaft. The inner shaft and the outer shaft can synchronously rotate. The inner shaft can rotate in the outer shaft by a preset angle so that the inner shaft can have a first position and a second position relative to the outer shaft. The exhaust opening angle generated when the inner shaft is located at the first position is ahead of the exhaust opening angle generated when the inner shaft is located at the second position. When the inner shaft is located at the first position, the waste gas rocker arm can interfere with the exhaust rocker arm so that the exhaust closing angle can be the sameas the exhaust closing angle generated when the inner shaft is located at the second position. When the inner shaft and the outer shaft are located at the first position, the waste gas rocker arm caninterfere with the exhaust rocker arm to hinder recovery of the exhaust rocker arm, and therefore an exhaust valve which is opened early can be normally closed through interference of the waste gas rocker arm and it can be ensured that waste gas is discharged from the exhaust valve.