The invention discloses a nickel-based high-temperature alloy oxidation-resistance and corrosion-resistant protective coating and a preparation technique thereof. The protective coating is prepared from three elements including Cr, Al and Y through a pack cementation method. The protective coating is prepared from, by weight, 5-10% of Cr, 10-20% of Al, 1-2% of Y2O3, 6-10% of NH4Cl and the balance Al2O3. The preparation technique comprises the steps that raw materials are weighed accurately according to the weight percentage for preparation of the protective coating; then ball milling and drying are conducted; the raw materials are placed into a crucible after being dried; the raw materials are placed in a muffle furnace after being sealed and charged; and the muffle furnace is heated for 40-60 min to the temperature of 1050-1070 DEG C, heat preservation is conducted at the temperature of 1050-1070 DEG C for 2-3 h, then the temperature is decreased to 600 DEG C with the furnace, the raw materials are taken out and cooled to the room temperature, and finally, the protective coating can be obtained through cleaning and drying. According to the protective coating, a Cr-Al-Y coboronising layer is prepared on the surface of the nickel-based alloy, the technical problem that the nickel-based alloy is poor in high-temperature resistance and corrosion resistance is solved, the preparation technique is stable and reliable, the coating is good in binding force, uniform in structure and compact, and the coating thickness is controllable; and the preparation technique has the advantages of being simple, convenient to operate, high in efficiency, low in cost, easy to implement and the like.