The invention discloses a methanol-to-olefin preparation gas separation process. According to the invention, a pre-C3-removing process is adopted, and an absorbent separation tower is arranged before a methane-removing tower, such that a material is preliminarily separated. Two streams of different absorbents are adopted in the methane-removing tower, and enter the tower from different positions on the upper part. A main absorbent is a tower kettle material from the absorbent separation tower, and the other stream of absorbent is C2, C3 or a mixture of hydrocarbons thereof from subsequent systems. Compared to prior arts, the process has the advantages of low investment, low energy consumption, high material recovery rate, simple operation, and the like.