The invention discloses a calorimeter and a system and method for measuring an absorbed dose. The calorimeter comprises a central ball and a hollow ball which is arranged to be concentric with the central ball. The hollow ball is sequentially provided with an inner case, an insulating layer and an outer case from the inside to the outside. The interior of the central ball is provided with a first thermistor. A second thermistor is disposed between the insulating layer and the outer case. A lead wire of the first thermistor is connected with a wire through a through hole. The calorimeter, system and method can solve problems that a conventional calorimeter is long in measurement waiting time and has measurement errors in a measurement process, solves a problem of temperature drift caused by the continuous heating of the first thermistor through combining with a circuit switcher, improves the measurement precision of the resistance value of a thermistor, and achieves the precise measurement of the absorbed dose of a pulse neutron and gamma ray mixed field quickly and effectively.