To　obtain　the　effective　purification　performance　in　wastewater　treatment　process　(WWTP),　the　optimal　control　is　an　important　method　to　guarantee　the　effluent　quality　reaching　the　standard　and　improve　the　treatment　efficiency.　The　concentrations　of　dissolved　oxygen　(DO)　and　nitrate　nitrogen　(NO3-N)　are　primary　metrics　that　impact　effluent　quality,　which　is　need　to　be　stably　tracking　controlled　for　achieving　optimal　performance　in　WWTP.　Therefore,　the　double-layer　fuzzy　neural　network　(FNN)　based　optimal　control　method　with　multivariable　is　proposed.　Firstly,　considering　the　dynamic　characteristic　of　WWTP,　the　FNN　based　actor　network　is　exploited　to　approximate　the　unknown　dynamic　information.　Subsequently,　the　FNN　based　critic　network　is　integrated　to　minimize　the　cost　function　of　DO　and　NO3-N　concentrations,　which　is　composed　of　the　control　error　and　the　control　variable.　Then,　to　guarantee　the　stability　of　the　optimal　controller,　the　Lyapunov　function　is　constructed　through　backstepping　method　to　analyze　the　control　system　performance.　Finally,　the　optimality　and　effectiveness　of　the　control　system　with　multivariable　are　verified　via　the　simulation　experiments　in　benchmark　simulation　model　1.　©　1993-2012　IEEE.　All　rights　reserved.