Based on the analysis of formation and variation characteristics of oxide layers in ELID grinding, a new measurement principle and method for oxide layer measurement in ELID grinding was proposed. The thickness of the oxide layer was obtained based on measurement both outside surface and inner surface of the oxide layer by laser sensor and eddy current sensor. Calculation methods for measurement of the oxide layer in different ELID grinding periods were presented. In order to verify the correctness of the measurement principle and measurement method, evaluation experiments were down. Results show that the precision of the measurement is sufficient to be applied in ELID grinding.