A method of preparing a polyunsaturated fatty acid-calcium, comprising the following step: (i) dissolving a water-soluble calcium compound material or a mixture of several water-soluble calcium compound materials in an appropriate amount of water, to obtain an aqueous solution of calcium compound; wherein the water-soluble calcium compound material is selected from the group consisting of calcium acetate, calcium lactate, calcium chloride, calcium nitrate, calcium citrate, and calcium fumarate; (ii) adding the aqueous solution of calcium compound to a polyunsaturated fatty acid material at -20∼100°C of temperature; the polyunsaturated fatty acid material comprises one or more of the following substances: a polyunsaturated fatty acid with a formula wherein R 1 is a C 6 ∼C 40 alkenyl group, R 2 is H or a C 1 ∼C 4 alkyl group; and a polyunsaturated fatty acid with a formula wherein R 3, R 4, R 5 are a hydroxyl or a C 1 ∼C 4 carboxylic acid group or a C 6 ∼C 40 carboxylic acid group containing one or more double bonds; R 3, R 4 and R 5 can be the same or different; and R 3, R 4 and R 5 cannot be simultaneously a hydroxyl group or a C 1 ∼C 4 carboxylic acid group; (iii) filtrating to obtain a solid of polyunsaturated fatty acid-calcium after completion of the reaction; and (iv) drying and crushing the solid of polyunsaturated fatty acid-calcium, to obtain a free-flowing polyunsaturated fatty acid-calcium product. (i) dissolving a water-soluble calcium compound material or a mixture of several water-soluble calcium compound materials in an appropriate amount of water, to obtain an aqueous solution of calcium compound; wherein the water-soluble calcium compound material is selected from the group consisting of calcium acetate, calcium lactate, calcium chloride, calcium nitrate, calcium citrate, and calcium fumarate; (ii) adding the aqueous solution of calcium compound to a polyunsaturated fatty acid material at -20∼100°C of temperature; the polyunsaturated fatty acid material comprises one or more of the following substances: a polyunsaturated fatty acid with a formula wherein R 1 is a C 6 ∼C 40 alkenyl group, R 2 is H or a C 1 ∼C 4 alkyl group; and a polyunsaturated fatty acid with a formula wherein R 3, R 4, R 5 are a hydroxyl or a C 1 ∼C 4 carboxylic acid group or a C 6 ∼C 40 carboxylic acid group containing one or more double bonds; R 3, R 4 and R 5 can be the same or different; and R 3, R 4 and R 5 cannot be simultaneously a hydroxyl group or a C 1 ∼C 4 carboxylic acid group; a polyunsaturated fatty acid with a formula wherein R 1 is a C 6 ∼C 40 alkenyl group, R 2 is H or a C 1 ∼C 4 alkyl group; and a polyunsaturated fatty acid with a formula wherein R 3, R 4, R 5 are a hydroxyl or a C 1 ∼C 4 carboxylic acid group or a C 6 ∼C 40 carboxylic acid group containing one or more double bonds; R 3, R 4 and R 5 can be the same or different; and R 3, R 4 and R 5 cannot be simultaneously a hydroxyl group or a C 1 ∼C 4 carboxylic acid group; (iii) filtrating to obtain a solid of polyunsaturated fatty acid-calcium after completion of the reaction; and (iv) drying and crushing the solid of polyunsaturated fatty acid-calcium, to obtain a free-flowing polyunsaturated fatty acid-calcium product.