Abstract: According to the varying law of the marine pressurized water reactor (PWR) critical control rod positions, the solid burnable poison and the physical state of fuel rod with the increase of the burn-up time, the influence of these changes on the reactor temperature coefficient was analyzed. The varying law of marine PWR temperature coefficient with fuel consumption was identified. That is, in full burn-up life, the marine PWR-temperature coefficient is negative, while the absolute value will decrease as the burn-up time increases.