Based on the effective mass approximation and envelope function theory, the exciton binding energy in a single InAs  /  In_xAl_{1  −  x}As quantum well is calculated by the variational method under the applied electric field and laser field. The effects of material composition, well width, laser parameters, and electric field intensity on the exciton binding energy are calculated. The results show that the confinement potential is distorted by the laser field and the barrier is tilted by the electric field. The exciton binding energy is reduced by the presence of laser field or electric field. It is also shown that the exciton binding energy increases with the decrease of the indium component within a certain range. In addition, the effect of the well width on the exciton binding energy is not linear, and the exciton binding energy increases to a maximum first and then decreases with the decrease of the well width. The binding energy of excitons depends on the interaction of several parameters.