The influences of the temperature on the effective mass of the exciton, for which the electron (hole) is strongly coupled with interface-optical phonons but weakly coupled with bulk-longitudinal-optical phonons in a quantum well, are studied by means of Tokuda’s improved linear combination operator and a modified Lee-Low-Pines transformation method. The resuls indicate that the effective mass (M*ex－LO) of the exciton, which is induced by the electron (hole) weakly coupled with bulk-longitudinal-optical phonons, will increase with the well width (N) increasing and first increase and then decrease, finally tends to a stable value with the distance between the electron and the hole (ρ) increasing. The influence of temperature on M*ex－LO and its changing with N and ρ is obvious. The change of M*ex－LO with T is strongly related to the quantum-size effect. The effective mass M*ex－IO of the exciton, which is induced by the electron (hole) strongly coupled with interface-optical phonons, will decrease with increasing N, increase with increasing T and first increase and then decrease, finally tends to a stable value with increasing ρ.But the influence of temperature on M*ex－IO and its changing with N and ρ is not obvious.