In　this　article,　the　element　distribution　was　optimized　by　introducing　isothermal　annealing　for　the　(Sm0.4Er0.6)2Co17　alloys　and　magnet　with　remanence　temperature-coefficient　(20-150　degrees　C)　of　-0.00087　%/degrees　C　and　coercivity　of　30.0　kOe　was　finally　prepared,　along　with　(BH)max　of　18.1　MGOe.　The　low　remanence　temperaturecoefficient　reveals　that　the　(Sm0.4Er0.6)2Co17　magnet　can　provide　a　steady　magnetic　flux　suitable　for　application　in　precision　instruments.　In　addition,　the　composition　distribution　in　the　magnet　was　analyzed　in　detail,　and　the　contribution　of　the　non-uniform　distribution　of　Er　to　the　coercivity　was　revealed　through　micromagnetic　simulations.　The　results　of　micromagnetic　simulations　confirm　that　the　concentrated　distribution　of　Er　in　the　intracellular　phase　is　beneficial　for　maintaining　high　coercivity　of　(Sm0.4Er0.6)2Co17　magnets.　This　finding　can　provide　effective　reference　for　the　development　of　rare-earth　permanent　magnets　with　outstanding　temperature　stability,　and　promote　the　development　of　precision　instruments.