The invention relates to an environmental-protection type PVC/ABS plastic alloy material and a preparation method thereof. The alloy material comprises the following components by mass percent: 20-80% of PVC resin, 3-50% of ABS resin, 1-2.3% of stabilizing agent, 0.3-0.9% of lubricant, 5-40% of plasticizer and 5-20% of active calcium carbonate powder. In the invention, PVC/ABS plastic alloy produced and prepared by utilizing a clean process not only has the advantages of impact resistance, low-temperature resistance, easy forming and processing and the like of the ABS resin but also has the advantages of fire retardancy, corrosion resistance, weather resistance, scrub resistance, low price and the like of the PVC, so that an alloy material with high performance-price ratio is obtained andcan be applied to various industries of electronics, instruments, automobiles, household electrical appliances, cable sheaths and the like. The invention provides a clean production and preparation process of the PVC/ABS plastic alloy. The production process increases the grinding and milling technology of a sealed type mechanical mill, executes totally enclosed type production, solves the dust pollution, reduces the energy volatilization, saves the mixing time, realizes zero discharge and has no three-waste pollution and maximum energy saving and discharge reduction.