The invention relates to a method for separating and purifying human immunoglobulin from a component I+III of blood plasma, and aims to provide a high-efficiency method for recovering high-purity human immunoglobulin. According to the technical scheme provided by the invention, the method comprises the following steps of: a, fully dissolving component I+III precipitate; b, precipitating with octylic acid and removing lipid and a part of impurity protein to prepare IgG (Immunoglobulin G); c, purifying through anion exchange column chromatography; and d, collecting flow-through liquid, performing membrane nanofiltration, ultrafiltration and concentration, preparing the human immunoglobulin, sterilizing and packaging. The method has the beneficial effects of capability of being operated at the room temperature, simple and short steps, high yield, low energy consumption and high output and is suitable for mass production; comprehensive utilization of the blood plasma is fully realized; the time of the entire production process is shortened; the cost is reduced; extremely considerable economic benefit can be produced; the safety of a product is guaranteed by using two virus inactivation/elimination methods of different mechanisms; the environmental pollution is avoided; and the method has high economic and social values.