The JYSR series three blade Roots blower (dry type Roots vacuum pump) not only has the hard exhaust characteristics of a general three blade Roots blower (hereinafter referred to as the blower or fan for both the fan and dry type vacuum pump) (that is, when there is a change in pressure or vacuum degree, the flow rate of the fan's inlet state decreases), but also has its advantages in that the medium conveyed by the fan does not contain oil stains. It adopts a world shaped inlet and outlet and an internal reflux structure, Effectively delaying the backflow impact of high-pressure gas, resulting in low fan vibration and significantly reduced noise.