The invention relates to a method for inserting a nucleus in a pear mussel. The method comprises the following steps: 1, pearl delivery pipe selection: selecting a pearl delivery pipe of a corresponding length and a corresponding inner diameter according to the size of the mussel in which the nucleus needs to be inserted and the size of the inserted pearl nucleus; 2, steel needle selection: selecting a matched steel needle according to the pearl delivery pipe which is selected in step 1, wherein the inserting length of the steel needle is regulated by a regulating clip; 3, nucleus delivery: opening a mussel mouth, feeding the pearl delivery pipe in the nucleus inserting position of the visceral mass of the mussel, inserting the steel needle of which the inserting length is regulated in the pearl delivery pipe, scratching the visceral mass, taking out the steel needle, and then sending the pearl nucleus to the visceral mass through the pearl delivery pipe. The method has the beneficial effects that the method for inserting the nucleus in the fresh water pear mussel is simple and feasible, the positioning of nucleus inserting is accurate, the wound on the surface of the visceral mass of the pearl mussel is small, and post-operation recovery time is short; the current survival rate of the nucleus-inserted fresh water pear mussel is increased, and the quality of the nucleus fresh water pear mussel is improved.