Abstract: A new model of the evaporation of a pure liquid layer underlying its own vapor is proposed and analyzed. The liquid layer is subjected to horizontal temperature gradient under microgravity condition. The thermocapillary convection is coupled with the evaporation, adding complication in the interfacial mass and heat transfer. An analytical expression for temperature distribution is given in pure evaporation case without considering thermocapillarity. For the case of both evaporation and thermocapillary convection, a finite difference algorithm is developed to solve simultaneously the thermal and flow fields in the liquid layer at various evaporation Biot number and Marangoni number until the steady state solution is achieved. The influence of evaporation Biot number and Marangoni number on the interfacial mass and heat transfer has been discussed. Three regimes of the coupling between evaporation and thermocapillary convection are found and explained from our numerical results.