The utility model provides a self-expandable packer with an outburst prevention function. The self-expandable packer comprises a base pipe, a self-expandable rubber sleeve and two end rings. The self-expandable rubber sleeve and the end rings sleeve the base pipe, the two end rings are correspondingly adjacent to two ends of the self-expandable rubber sleeve, supporting ring assemblies are arranged between the end rings and the self-expandable rubber sleeve and comprise metal limiting rings and supporting rings made of rubber, the metal limiting rings and the supporting rings sequentially sleeve the base pipe, one end of each metal limiting ring is in contact with the inner end of the corresponding end ring, the other end of each metal limiting ring is adjacent to one end of the corresponding supporting ring, each end of the self-expandable rubber sleeve is reduced to form an outer conical surface, a ring lug is convexly arranged at the other end of each supporting ring and corresponds to the self-expandable rubber sleeve, the inner peripheral surface of each ring lug is an inner conical surface which is matched with the corresponding outer conical surface, and the ring lugs correspondingly sleeve the outer conical surfaces of the self-expandable rubber sleeve via the inner conical surfaces. The self-expandable packer has the advantages that the self-expandable packer is provided with the supporting ring assemblies, so that the self-expandable rubber sleeve can be effectively prevented from being axially expanded along annular spaces in expansion procedures, and sealing pressures can be obviously increased.