The invention provides an elastic-hard knife ring for hard rock excavation by a shield machine and a heat treatment method thereof. The knife ring is divided into A, B and C three regions from a knifeedge to a knife seat, the metallographic structure in the portion of the A region is a tempered martensite-based homogeneous hardened layer, the metallographic structure in the portion of the C region is mainly tempered troostite, and the portion of the B region is a transitional area. First, the knife ring is entirely quenched and entirely tempered, and then the knife seat portion of the knife ring is partially tempered so that the knife edge portion of the knife ring is mainly the tempered martensite and the knife seat portion is the tempered troostite. The high-strength knife edge and theelastic knife seat are matched so that the knife ring has high wear resistance, anti-buffering capacity and impact toughness; meanwhile, the knife edge has residual compressive stress so that the anti-fatigue ability of the knife edge is increased and the knife ring has a longer service life and rock breaking ability.