Exploitation of squirrel-cage induction motors (SCIMs) is inevitably accompanied by the appearance of the transient processes that critically impact the condition and operation of electrical machines. In the study of transients in induction motors must consider that during the start-up, the rotor parameters (resistance and inductance) are changing due to the skin effect. The current paper is dedicated to the research of the direct start-up of the SCIM with due account for of the current’s displacement in the rotor slots. The current paper is dedicated to the research of the different methods for calculations the rotor’s variables parameters. The resistance and inductance of the rotor were calculated in different methods. The conclusion about the need to consider the skin effect in the calculations of the rotor’s variables parameters is given.