The invention relates to a hydraulic oil tank breather with a pre-compression type centrifugal separation mechanism. The hydraulic oil tank breather comprises an installation base, a shell body, a connecting base, a top cover and a cotton net filtering core. The installation base is provided with an exhaust valve assembly and an air inlet valve assembly. The exhaust valve assembly comprises an exhaust valve core, an exhaust spring and an exhaust screw plug. The air inlet valve assembly comprises an air inlet valve core, an air inlet spring and an air inlet screw plug. The hydraulic oil tank breather further comprises the centrifugal separation mechanism arranged between the shell body and the connecting base. According to the hydraulic oil tank breather with the pre-compression type centrifugal separation mechanism, the purposes are achieved, specifically, the exhaust valve assembly and the air inlet valve assembly are arranged on the installation base, a certain positive pressure in an oil tank can be maintained, and the normal air inlet effect can be ensured; oil particles in exhaust can be effectively adsorbed on the inner wall of a centrifugal separation barrel by arranging the centrifugal separation mechanism, and the concentration of the oil particles reaching the cotton net filtering core is reduced; and the cotton net filtering core is arranged in the top cover, the oil particles in the exhaust can be effectively absorbed, and thus the situation that the appearance of the hydraulic oil tank is affected due to the fact that the oil particles flow out from an air outlet hole of the breather and pollute the environment is avoided.