Abstract: The dependence of the exciton-light coupling on the size of a quantum well in an external electric field is theoretically analyzed. It is shown that in a sufficiently strong field, an increase in the width of the well leads to weakening of the exciton-light coupling in comparison with narrower wells. Numerical calculations of the longitudinal-transverse exciton splitting are performed for wide ranges of the electric field strength and quantum well width. The analysis of the obtained data allowed us to derive expressions describing the dependences of the exciton-light coupling on both the magnitude of the applied electric field and the well width.