Abstract: This paper presents the temperature field distribution model and wellbore steam flow model of steam injection well applying gas-liquid two-phase flowing theory and heat conduction principal,and then introduces the relevant calculation software for temperature field distribution.In order to obtain the accurate steam flowing parameters and temperature field distribution during steam injection,two models consider the effect of downhole packer and insulated tubing,and use the more reasonable bottom hole heat transfer boundary conditions.The step integration finite element method,which has advantages of good boundary suitability and high calculating precision,is used in analysis of transient formation temperature field.This paper gives an introduction on computing theory and method,and presents the skills that conduce to increase calculating precision,The software(ISTAP) has good practicality.