The present invention relates to a method of preparing a positive electrode active material precursor for a lithium secondary battery in which particle size uniformity and productivity may be improved by using three reactors, a method of preparing a positive electrode active material for a lithium secondary battery by using the above-prepared positive electrode active material precursor for a lithium secondary battery, and a positive electrode for a lithium secondary battery and a lithium secondary battery which include the above-prepared positive electrode active material for a lithium secondary battery.