The invention discloses a casting mold rubber and application thereof, belonging to the technical field of casting mold detection. The casting mold rubber is compounded from silicon rubber and a curing agent. Under the synergistic actions of the silicon rubber and curing agent within a restricted proportioning range, the prepared casting mold rubber can be quickly cured at normal temperature, has the self-lubricating effect, can smoothly implement mold release on various metal and non-metal substrates without any mold release agent, has the advantages of small curing shrinkage, favorable isotropy, favorable flowability and flat and compact molded surface, has no pores, cracks, impurities, shrinkage cavities or other defects, and can actually copy various chamfers which can not be measured easily. When being used for chamfer detection, the casting mold rubber can be cured and molded at normal temperature within 4 hours, can smoothly implement mold release without any mold release agent, can be used for rubber compound mold technological detection on large-batch parts outdoors, is safe and reliable to use, and has huge economic and social benefits.