NOVELTY - Processing rhizoma coptidis seed oil comprises (i) drying rhizoma coptidis mature seed and pressing to obtain crude oil and oil cake, (ii) washing rhizoma coptidis crude oil using aqueous acid solution for 1-3 times, (iii) alkali washing the crude oil using aqueous alkali solution of pH 8-11 for 1-3 times, (iv) washing alkali washed crude oil with pure water, and (v) placing crude oil in cold storage, allowing for precipitation, separating yellow viscous precipitate through centrifugation or filtration to obtain light yellow clear and transparent rhizoma coptidis seed oil.    USE - The rhizoma coptidis seed oil is useful in preparing cardiovascular and cerebrovascular disease and diabetes prevention healthcare product, in preparing edible oil, linoleic acid and oleic acid (all claimed).    ADVANTAGE - The method produces yield of 33-37%, is simple, economical and environmentally friendly, and produces product with good quality. The oil has linoleic acid content of 43-45%, oleic acid content of 37-40% and total unsaturated fatty acid content of 82-86.5%.    DETAILED DESCRIPTION - Processing rhizoma coptidis seed oil comprises (i) drying rhizoma coptidis mature seed and pressing to obtain crude oil and oil cake, (ii) washing rhizoma coptidis crude oil using aqueous acid solution for 1-3 times, where the aqueous acid solution is edible acid solution of pH 1-4 and the adding amount of aqueous acid solution is 0.5-2 times volume of crude oil, (iii) alkali washing the acid washed crude oil using aqueous alkali solution of pH 8-11 for 1-3 times, where the adding amount of aqueous alkali solution is 0.5-2 times volume of crude oil, (iv) washing alkali washed crude oil with pure water until pH of aqueous phase is 7-7.5, and (v) placing crude oil in cold storage, allowing for precipitation, separating yellow viscous precipitate through centrifugation or filtration to obtain light yellow clear and transparent rhizoma coptidis seed oil. An INDEPENDENT CLAIM is also included for rhizoma coptidis seed oil, prepared by the above method.