The invention provides a control method for improving the electrical efficiency of an electric locomotive. The method includes the following steps that (1) actually measured locomotive wheel circumference traction force Fk actual measurement, the actually measured locomotive operation speed Vactual measurement, the actually measured primary side current Iprimary side actual measurement and the actually measured net voltage Unet actual measurement of the electric locomotive are obtained, and then the actually measured locomotive efficiency value etaactual measurement is calculated according to the formula shown in the specification; and (2) according to the actually measured locomotive efficiency value etaactual measurement, switching of traction motors is controlled, so that the locomotive speed is made to reach a set speed, and the locomotive efficiency value is made to reach a set efficiency value. According to the control method, the load rate level of each traction motor of the locomotive can be adjusted automatically, the traction motors are made to work in the optimal range, and on the premise of ensuring safe operation, the operation electrical efficiency of the locomotive is made the highest; from locomotive operation data actually collected by following the locomotive, it can be seen that after the method is used, the 80% energy-saving effect can be achieved, tens of millions of yuan of electricity expenditures can be saved for the railway administration every year.