Combination valve for ventilation and pressurization of oil tank

The invention discloses an oil tank ventilation and pressurization combination valve which comprises a shell and a cover, an air entraining cut-off valve assembly, an unloading type pressure reduction valve assembly, a ventilation valve assembly, a safety valve assembly and an electromagnetic valve assembly are arranged in the shell and the cover, the shell and the cover are connected through screws, and the shell is provided with connecting ports communicated with the atmosphere and an oil tank respectively. A pipe nozzle is further arranged on the shell, an air entraining pressurization opening is formed in the pipe nozzle, the pipe nozzle is connected with an air entraining cut-off valve assembly, the air entraining cut-off valve assembly is connected with an electromagnetic valve assembly through a guide pipe, an unloading type pressure reduction valve assembly is communicated with an oil tank through a second connecting opening, and a safety valve assembly is communicated with the second connecting openi