A device and method for monitoring freezing-thawing damage of an underwater concrete member in situ. A main structure includes an upper link, concrete member, transverse sealed box, longitudinal sealed box, movable guide rod, probe launching box, multichannel data collector, frequency modulation transmitter, computer, auxiliary wheels, lower link, and a wireless temperature sensor. A process includes four steps: launching of a probe, collection of data, calculation of an elastic modulus, and evaluation of freezing-thawing damage. The device is simply structured, easy to operate, and can be reused, and provides power for launching the probe by non-contact force transmission by using high-strength magnets of the same pole, resolving the sealing problem, and calculates the elastic modulus of the concrete member by using acceleration data obtained by a probe, so as to obtain a loss amount of the elastic modulus, thereby performing real-time in-situ monitoring for freezing-thawing damage of an underwater concrete member.