Due　to　the　influence　of　outdoor　climate　and　indoor　human　activities,　the　moisture　accumulation　of　building　enclosure　structure　will　lead　to　the　growth　of　mould　on　the　interior　surface　of　the　wall,　damage　the　building　structure　and　endanger　human　health.　Taking　an　office　building　in　Dachangshan　Island　of　Dalian,　a　cold　area　in　North　China,　as　an　example,　the　outdoor　relative　humidity　is　high,　and　the　temperature　difference　between　indoor　and　outdoor　is　large　during　the　heating　period,　which　is　easy　to　cause　the　increase　of　moisture　content　of　the　enclosure　structure　and　the　growth　of　mould.　This　study　focuses　on　the　influence　of　the　heat　and　moisture　transfer　characteristics　of　the　office　building　wall　on　the　growth　process　of　mould　on　the　interior　surface　of　the　building.　The　dominant　fungi　of　indoor　air　and　wall　surface　werePenicilliumandCladosporium.WUFI　software　was　used　to　simulate　the　heat　and　moisture　transfer　and　the　growth　process　of　mould　on　the　inner　surface　of　the　wall.　The　results　show　that　the　relative　humidity　of　the　air　micro　layer　on　the　inner　wall　surface　of　the　office　building　reaches　more　than　80%　at　the　beginning　of　heating　period　in　November　every　year,　the　mould　hypha　grows　significantly　in　December　and　brings　pollution　risk.　Finally,　the　relative　humidity　drops　below　70%　after　the　heating　period　is　over　in　April,　and　the　mould　stops　growing.　The　main　reason　for　this　phenomenon　is　that　the　condensation　interface　in　the　wall　structure　during　the　heating　period　leads　to　the　accumulation　of　water　in　the　wall,　which　is　then　transmitted　to　the　wall　surface　through　the　wall　pores,　thus　increasing　the　moisture　content.　This　method　provides　a　r　eliable　way　for　the　numerical　simulation　of　indoor　mould　growth　risk.