The invention discloses a special coating process of a cargo tank of a product tanker/chemical tanker. The process adopts an integral method instead of an upper and lower part method and has the effects of meeting the construction requirement of the special coating, shorting the special coating period, improving the special coating efficiency, lowering the special coating cost and ensuring smooth special coating construction. The process specifically comprises the concrete steps of protection of fittings and piping systems in a cabin, scaffold setting up in the whole cabin, advance sand blasting in the whole cabin, main sand blasting in the whole cabin, dust absorption and surface treatment inspection in the whole cabin, first coating of the whole cabin, cabin bottom protection, upper part painting, upper part film painting and repairing, upper part film painting inspection, scaffold dismantling, lower part protection removal, treatment of the support point of the lower scaffold; lower surface cleaning and inspection; and lower part painting, lower part film painting and repairing and lower part film painting inspection. The process has multiple considerable effects such as high efficiency, low cost, energy conservation and the like and has the effects of not only ensuring smooth completion of special coating of the 110,000-ton large product tanker but also creating considerable economic and social benefits.