The　3-μ　m　mid-infrared　laser　has　significant　application　prospects　and　value　in　scientific　and　technical　applications　such　as　laser　medicine,　biomolccular,　and　optoelectronic　countcrmcasures.　This　paper　describes　the　generation　of　mid-infrared　lasers　and　the　characteristics　of　various　mid-infrared　lasers.　Based　on　the　Er3+　ion　level　structure,　the　main　conversion　process　and　existing　problems　of　erbium-doped　mid-infrared　lasers　arc　discussed　herein.　The　research　progress　of　erbium-doped　mid-infrared　lasers　based　on　different　substrates　is　summarized.　The　problems　that　need　to　be　solved　and　the　possible　technical　approaches　for　high-efficiency,　high-power　erbium-doped　mid-infrared　lasers　arc　envisioned.　©　2019　Universitat　zu　Koln.　All　rights　reserved.