The invention provides an environmentally-friendly strong sealing oil-based drilling fluid. The environmentally-friendly strong sealing oil-based drilling fluid is based on a base liquid, and comprises 10-20wt% of an aqueous solution of calcium chloride, 1-2wt% of a main emulsifier, 1-2wt% of an auxiliary emulsifier, 2-3wt% of a wetting agent, 3-5wt% of organic soil, 2-3wt% of calcium oxide, 2-4wt% of a sealing agent, 2-4wt% of a filtrate reducer, and 0-150wt% of a weighting material. The drilling fluid can effectively seal shale formation, improves the stability of a borehole wall, and reduces the pollution to environment; and the novel weighting material used in the invention has small influences on the rheological performance of the oil-based drilling fluid and reduces damages to reservoirs.