In　this　study,　desilication　treatment　using　alkali　etching　was　applied　to　ZSM5molecular　sieves　with　four　different　silicon-aluminum　ratios　to　investigate　the　difference　of　their　ammonia　nitrogen　adsorption.　Their　changes　in　crystal　structure,　surface　morphology,　internal　element　composition　and　connection　mode　after　desilication　were　examined　with　scanning　electron　microscopy,　X-ray　diffraction　analysis,　X-ray　fluorescence　spectroscopy,　and　Fourier　transform　infrared　spectroscopy.　The　mechanism　of　the　desilication　effect　on　improving　the　adsorption　of　ammonia　nitrogen　by　molecular　sieves　was　then　analyzed.　The　results　indicated　that　after　desilication　treatment,　the　mesoporous　specific　surface　area　and　specific　pore　volume　of　the　molecular　increased,　and　the　pore　size　distribution　was　broaded,　the　structure　of　the　molecular　sieve　remained　intact　and　the　grain　morphology　became　clear　and　regular,　associated　with　enhanced　ion　exchange　capacity　and　Si/AlO4　structure.　The　molecular　sieve　desilication　by　alkali　etching　had　multiple　effects　such　as　desilication　of　skeleton,　the　aluminum　supplementation　of　skeleton,　and　the　tunnel　dredging.　These　led　to　decreased　silicon-aluminum　ratio　and　increased　number　of　active　sites　in　the　molecular　sieve,　meanwhile,　decreased　the　diffusion　resistance　of　ammonia　ion,　which　then　resulted　in　improved　ammonia　nitrogen　adsorption　performance.　After　desilication,　the　ammonia　nitrogen　adsorption　by　molecular　sieve　was　greatly　enhanced,　while　more　significant　improvement　was　observed　for　molecular　sieve　with　originally　higher　silicon-aluminum　ratio.　while　its　equilibrium　adsorption　capacity　of　ammonia　and　nitrogen　increased　from　5.81mg/g　to　10.44mg/g,　with　an　increase　of　79.7%　being　reached.　In　summary,　the　desilication　treatment　could　provide　an　effective　technical　alternative　to　use　molecular　sieve　for　the　deep　denitrification　of　wastewater　treatment　plant　effluent.　©　2019,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.