Abstract: To clearly understand the distribution patterns of thermal parameters during steam injection in horizontal wells completed with slotted liners and to establish a theoretical basis for the optimization of completion processes,a numerical model for the distribution of steam pressure,temperature and dryness in horizontal well while steam injection was developed according to the law of conservation of mass,momentum and energy.Next,the model was solved by iterating both steam pressure and dryness increments. On this basis,the case analysis was made to identify the distribution of thermal parameters of steam along horizontal wellbore and the impacts of slotted liner parameters on the patterns of distribution. The results show that after passing through a horizontal section of 300 m,the steam pressure,temperature and dryness were reduced by 5.8 kPa,0.035 ℃ and 0.128,respectively. When the width,length and density of slot were increased respectively from 0.2 mm to 0.4 mm,100 m to 140 m,and 200 slots/m to 360 slots/m,the steam absorption length would be reduced by 90 m,100 m and 70 m. Within the steam absorption length in the horizontal section,the steam pressures were decreased by 1.5 kPa,1.74 kPa and 1.38 kPa,whereas steam dryness increased by 0.03,0.06 and 0.056,respectively. Steam pressure,temperature and dryness display non-linear reduction in quadratic polynomial relationsalong the horizontal wellbore. Therefore,the increase in slot width,length and density will reduce the drop rate of steam pressures,increase the drop amplitude of steam dryness,and shorten the length of steam-absorption in horizontal section.