Currently,　microchannel　heat　exchangers　(MCHXs)　are　widely　employed　in　refrigeration　and　heat　pump　systems　due　to　their　advantages　of　being　more　efficient,　smaller　in　size,　lower　refrigerant　charge,　and　cheaper　price.　However,　when　used　as　evaporators,　MCHXs　have　the　issues　of　a　faster　frosting　rate　and　frost　melt　water,　condensate　that　is　more　difficult　to　remove　than　fin-and-tube　heat　exchangers.　This　review　paper　focuses　on　the　research　progress　on　the　thermal-hydraulic　and　drainage　performance　of　MCHX　under　frosting,　defrosting,　and　wet　conditions　from　the　year　2000–2022.　First,　experimental　research　on　the　frosting　and　drainage　characteristics　of　MCHX　is　summarized　and　analyzed　in　periodic　frosting　and　defrosting　conditions.　Then,　three　typical　methods　for　improving　the　frosting　and　defrosting　performance　of　MCHX　are　introduced.　Moreover,　empirical　correlations　and　simulation　models　developed　to　predict　the　frosting　and　defrosting　characteristics　of　MCHX　are　discussed.　Uneven　frost　layer　distribution　should　be　considered　in　the　frosting　model　and　the　effect　of　drainage　characteristics　on　defrosting　performance　should　be　considered　in　the　defrosting　model.　The　thermal-hydraulic　and　drainage　performance　of　MCHX　under　wet　conditions　is　also　reviewed.　First,　methods　for　testing　real-time　condensate　retention　are　introduced.　Then,　the　parameters　affecting　the　thermal-hydraulic　and　drainage　characteristics　of　the　MCHX　are　analyzed.　Based　on　the　above　research,　two　methods　for　improving　the　performance　of　MCHX　under　wet　conditions　are　introduced.　Empirical　correlations　and　numerical　models　for　predicting　thermal-hydraulic　performance　under　wet　conditions　are　classified　and　compared.　A　novel　one-dimensional　numerical　model　based　on　the　fin　theory　combined　with　the　moving　boundary　technique　can　accurately　capture　the　actual　dehumidification　state　with　a　small　computational　cost.　The　main　conclusions　regarding　the　thermal-hydraulic　and　drainage　performance　of　MCHX　based　on　the　open　literature　are　presented.　Finally,　some　research　initiatives　and　vital　improvement　measures　are　suggested　for　future　studies.　This　review　aims　to　serve　as　a　reference　guide　for　the　thermal-hydraulic　and　drainage　characteristics　studies　of　MCHX　under　frosting,　defrosting,　and　wet　conditions.　©　2022　Elsevier　Ltd