The reactor with a negative temperature coefficient of reactivity has inner stability, which is a important symbol of inherent reactor safety. During the reactor start-up Commissioning Stage C for CARR, the measurement of equivalent temperature coefficient of reactivity is a important experiment by the way of measuring the reactivity change resulting of the equivalent temperature variation in the reactor core. During the reactor start-up Commissioning Stage C for CARR, the measurement of the equivalent temperature coefficient of reactivity is a important experiment by the way of measuring the reactivity change resulting of the equivalent temperature variation in the reactor core.