Expansion microscopy (ExM) is a newly developed technology in recent years that enables nanoscale imaging under conventional microscopes. Herein, we report an aptamer-based ExM imaging strategy. A nucleus-targeting aptamer Ch4-1 was chemically labeled with a dye and an acrydite at each end to perform the functions of molecular recognition, fluorescence reporting, and gel anchoring. After binding cell nucleus, the dual labeled aptamer Ac-Ch4-1-FAM directly participated in gelation and anchored in polyacrylamide gel. After expanding the gel, high-resolution imaging was achieved by confocal microscopy. Multicolor ExM imaging was also realized by combining Ac-Ch4-1-FAM, antibodies and fluorescent dyes. This aptamer-based ExM could clearly image the chromatin morphology at different mitotic stages. The expansion process is simple and the aptamer labeling is easy. The aptamer-based ExM holds great promise in super-resolution imaging of cells and tissues.