In　order　to　improve　the　reuse　of　phosphorus　adsorbent　Mg/Al-LDO,　the　regeneration　effects　of　roasting　one-step　regeneration　and　desorption-roasting　two-step　regeneration　were　compared.Based　on　XRD　and　FTIR　spectrum　analysis,　the　changes　of　crystal　structure　and　interlayer　anionof　the　adsorbentwere　analyzed,　and　the　regeneration　mechanism　of　Mg/Al-LDO　and　reasons　for　the　declining　regenerationratewere　then　discussed.　The　results　indicated　thatdesorption-roasting　two-step　regeneration　was　more　suitable　for　the　regeneration　of　Mg/Al-LDO,　with　the　following　optimum　regeneration　condition:　desorption　solution　of　NaOH-Na2CO3　mixture,　roasting　temperature　of　550　and　duration　of　6h.　It　was　found　that　the　primary　regeneration　rate　reached　95%,　but　the　regeneration　rate　dropped　to　67%　after　five　regenerations.　Thus,　a　problem　of　decreased　regeneration　rate　existed.　Based　on　the　adsorption　mechanism　of　Mg/Al-LDO　and　the　analysis　of　XRD　and　FTIR　spectrum,　the　reasons　for　the　declining　regeneration　rate　include　two　aspects:　(1)　incomplete　desorption　of　phosphate　due　to　the　chemical　adsorptionof　Mg/Al-LDO　led　toun-removed　residual　phosphate　in　the　crystal　under　high　temperature　calcination　that　still　occupy　the　adsorbent　adsorption　site;　(2)　the　conversion　of　Mg/Al-LDO　into　spinel(MgAl2O4)　after　several　high-temperature　calcinationsled　to　the　loss　of　adsorption　capacity.　©　2017,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.