Composite additive composition for refrigerating machine oil for screw-type ammonia refrigerating compressor and preparing method thereof

The invention discloses a composite additive composition for refrigerating machine oil for a screw-type ammonia refrigerating compressor. The composite additive composition is prepared from, by weight, 5%-70% of aromatic diluent, 0.1%-20% of antioxidant, 0.1%-10% of extrcme pressure anti-wear additive, 0.01%-5% of metal deactivator and 0.001%-0.2% of antifoaming agent, wherein the kinematic viscosity of the aromatic diluent at the temperature of 40 DEG C is 5 mm /s to 100 mm /s, and %CA is 4% to 60%. The refrigerating machine oil obtained after the composite additive composition is added for the screw-type ammonia refrigerating compressor has the excellent low temperature fluidity, oxidation stability, extreme pressure anti-wear property, metal corrosion resistance and foaming resistance, and can more efficiently and circularly work in the ammonia refrigerating compressor for a long life. In addition, through the composite additive composition, the refrigerating machine oil is moreeasy and efficient in produc