The invention relates to vacuum refining and provides a dry type mechanical vacuumizing device comprising an air intake pipe, an air discharge pipe and an exhaust pipeline. The exhaust pipeline comprises an exhaust branch. The exhaust branch comprises a first-grade dust collecting assembly, a roots pump set, a second-grade dust collecting assembly and a screw pump set, wherein the first-grade dustcollecting assembly, the roots pump set, the second-grade dust collecting assembly and the screw pump set sequentially communicate, the first-grade dust collecting assembly communicates with the intake pipe, and the screw pump set communicates with the air discharge pipe. A first-grade front stop valve is arranged on the part, between the first-grade dust collecting assembly and the air intake pipe, of a flow path. The invention further provides a vacuum refining system comprising the dry type mechanical vacuumizing device. According to the dry type mechanical vacuumizing device and the vacuum refining system, the first-grade dust collecting assembly and the second-grade dust collecting assembly are arranged at intake openings of the roots pump set and the screw pump set correspondingly and have different pressure differences, so that during work, the pressure difference between the roots pump set and a vacuum chamber cannot be excessively large, and the situation that the pressure inthe vacuum chamber cannot meet the pressure requirement of molten steel vacuum treatment is avoided.