The invention discloses a strength mismatching heat treatment process for a petroleum steel tube in a hardened and tempered state, belonging to the technical field of metal engineering materials. The process comprises first-stage whole tube hardening and tempering and second-stage tube end hardening and tempering. According to the process, the strength mismatching of the tube body and the tube ends of the petroleum steel tube in a hardened and tempered state can be realized, the strength and toughness of the tube ends are higher than those of the tube body, and the strength and toughness of transition zones between the tube ends and the tube body are higher than those of the tube body but lower than those of the tube ends, thus ensuring that the steel tube has the performance distribution of strength mismatching accompanied with the distribution of toughness mismatching. The distribution of strength mismatching eliminates the weak point that the tube ends of the existing product are prone to deform or even break due to stress concentration caused by thread structures, and improves the service safety of the steel tube.