The one-mode mean-configuration model proposed by Giesekus has been generalized to non-isothermal cases. The well-known viscosity-temperature equations can then be used to account for the effect oi temperature and thermal history on the stress tensor and obtain a constitutive equation that describes the non-isothermal rheological behavior of concentrated polymer solutions and polymer melts without the necessity of introducing any assumption of non-isothermal behavior into molecular models. The calculations of non-isothermal stress growing indicates that the constitutive equation gives a reasonable description of the non-isothermal rheological behavior of polymer liquids without the disadvantages involved in the constitutive equations proposed by the previous investigators.