The invention relates to a sodium alginate-flaky ZIF-8 hybrid composite membrane, and belongs to the field of membrane separation. At first, Zn(NO3)2 and 2-methylimidazole are used as raw materials, and flaky ZIF-8 is prepared in a water phase form through control of synthesis conditions; then, the prepared platy ZIF-8 is dispersed in a sodium alginate water solution to prepare a casting solution, after standing and defoaming, the casting solution spirally coats the surface of a porous polymer ultrafiltration membrane, after drying, the porous polymer ultrafiltration membrane is crosslinked with a calcium chloride solution, and after drying again, the sodium alginate- flaky ZIF-8 hybrid composite membrane is obtained. The hybrid composite membrane can be used for dehydration through pervaporation of an ethanol / water system. Through utilization of the second-dimensional structure and the porous structure of the flaky ZIF-8, the screening effect of the hybrid composite membrane on molecular transport is enhanced, so that the separation performance of the hybrid composite membrane is improved. The preparation process is simple, raw materials are easy to obtain, the structure is controllable, the large-scale preparation and amplification are convenient, and the sodium alginate-flaky ZIF-8 hybrid composite membrane has a good application prospect.