The invention discloses a method for extracting lithium and nickel cobalt from a waste lithium ion battery step by step, and belongs to the technical field of comprehensive recovery of lithium ion battery materials. The method comprises the following steps of splitting, crushing and screening a waste lithium ion battery to obtain a positive electrode material powder, carrying out reduction roasting on the positive electrode material powder with a carbon-containing reducing agent, size mixing the obtained calcine with water, adding a proper amount of calcium chloride or lime milk solution for reaction transformation, selecting lithium carbonate in the calcine to be extracted into the solution, thereby realizing separation with nickel, cobalt, manganese, iron, aluminum and phosphorus. The method can realize the preferential selective extraction of lithium, the obtained lithium solution is high in purity and lithium concentration, the extraction and impurity removal, evaporation and concentration processes are not needed, the recovery of lithium and the product preparation process are simple, the recovery rate is high, the energy consumption is low, and the environmental problem of high-concentration sodium salt wastewater is not present```.