The steady-state design and optimization for a methanol-to-olefin (MTO) process is studied. The MTO process is a novel route for light olefin production, especially ethylene and propylene. Comparing with the traditional way to produce olefins by steam cracking, this process offers benefits such as a more flexible range of ethylene-to-propylene ratio, higher selectivity toward light olefin, and mild reaction conditions. The design of the overall MTO process is divided into four sections, namely, reaction section, conditioning section, first separation section, and second separation section. After the design of each sub-part, optimization is performed, in which the design and operating variables are thoroughly investigated. By rigorous simulation, a more economically competitive design flowsheet of the overall MTO process is proposed.