The invention discloses a novel membrane fixing device for a microporous aerator. The microporous aerator comprises an elastic aeration membrane with micropores and a supporting seat. The aeration membrane is supported by the supporting seat, the supporting seat comprises a hollow ring base, a cross support arm and a central gas inlet pipe, the cross support arm is connected with the bottom surface of the hollow ring base, the central gas inlet pipe is connected with the tail end of the cross support arm, a ring surface of the hollow ring base is a protruded arc-shaped ring surface, a circle of concave clamp groove is formed in the outer edge of the hollow ring base, a circle of extension edge which is correspondingly clamped with the concave clamp groove is arranged at the outer edge of the supported aeration membrane and is tightly hooped by a hoop, an inward covered edge is arranged at the inner edge of the supported aeration membrane and covers the inner edge of the hollow ring base, a support clamp ring is arranged on the outer side of the covered edge, and the supported aeration membrane is compressed at the inner edge of the hollow ring base by the support clamp ring in a supported manner.