The　building　simulation　method　can　accurately　and　conveniently　predict　and　evaluate　the　indoor　environment　of　the　building,　thus　guiding　designers　and　residents　to　adopt　appropriate　ventilation　and　purification　strategies　to　improve　the　indoor　environment　of　the　building　and　reduce　energy　consumption.　However,　there　is　no　software　for　simulating　the　ventilation　strategy,　IAQ,　and　purification　equipment　operation　effect.　Therefore,　this　paper　independently　developed　the　indoor　air　quality　simulation　program-IAQ,　and　on　this　basis,　put　forward　the　idea　and　implementation　method　of　IAQ+DeST　joint　simulation.　Finally,　a　real　household　in　Tianjin　was　used　as　a　simulation　object,　and　the　indoor　PM2.5　concentration,　CO2　concentration　and　building　energy　consumption　under　natural　ventilation,　mixed　ventilation,　and　mechanical　ventilation　were　simulated　by　IAQ+DeST　combined　simulation　method.　Calculation.　The　results　show　that:　First,　the　relative　error　between　the　calculation　results　of　building　energy　consumption　and　the　results　of　EnergyPlus　calculation　is　within　the　acceptable　range,　thus　verifying　the　reliability　of　the　program.　Second,　the　mixed　ventilation　method　can　effectively　reduce　the　building　energy　consumption　under　the　premise　of　ensuring　indoor　air　quality　and　can　be　considered　for　application　in　Tianjin.　©　2020,　Springer　Nature　Singapore　Pte　Ltd.