A lossless equalization controller and a control method belong to the technical field of battery equalization control. The controller comprises a battery pack formed by a plurality of cells, an equalization switch control module, an equalization power control module, an equalization power transformation module, an equalization charging control module, a system power supply module and a master control module, wherein the system power supply module supplies power to the equalization switch control module, the equalization charging control module and the master control module. The controller has the advantages of rapid equalization speed, safe and reliable equalization process, low cost and easy promotion and application. The control method includes detecting battery equalization degree, equalizing laggard cells in the battery pack when the battery equalization degree is equal to or greater than 0.3%, detecting system fault, clearing system fault and other detection steps. The equalization precision is high, and the equalization process is safe and reliable.