The invention discloses a blast temperature control system and control method for last-stage blades of a low-pressure cylinder. The last-stage temperature measuring point of a last-stage moving bladeoutlet is provided with a low-pressure cylinder attemperation water atomizing spraying head set, the low-pressure cylinder attemperation water atomizing spraying head set controls water spraying flowthrough a low-pressure cylinder water spraying adjusting valve. According to the device, the temperature of the low-pressure cylinder last-stage moving blade outlet can be collected through a temperature measuring element and sent to the control system, the control system controls the opening degree of the low-pressure cylinder water spraying adjusting valve according to the temperature sent by the temperature measuring element, and control over the blast temperature of the last-stage long blades is achieved. According to the device, on the condition of small volume flow, the blast temperatureof the low-pressure cylinder can be monitored and controlled automatically, and operation safety of the low-pressure cylinder under the condition of the small volume flow is ensured.