The dry screw vacuum system is an oil-free vacuum unit composed of a Roots vacuum pump as the main pump and a screw vacuum pump as the front stage pump in series. The unit has high vacuum degree, wide working pressure range, high pumping efficiency, and is packaged in a box. The unit adopts an intelligent variable frequency control system, which starts quickly and can accurately control the unit performance in real time according to production needs, improve production stability, and meet the needs of high-end customers. The vacuum pumps used in the unit are insensitive to small amounts of dust, and have obvious advantages in applications containing small amounts of dust. The motors used in the unit are water-cooled motors with good heat dissipation and can avoid dust from motor fans. They are particularly suitable for the production process of single silicon in the photovoltaic solar energy industry and can meet the production needs of industries such as lithium batteries, semiconductors, photovoltaics, and lithium new energy.