The invention discloses a crystallization and drying system and method for radioactive waste liquid. Firstly, parameter values of a third temperature sensor at an air inlet of the bottom of a drying tank, a first temperature sensor at an air outlet of the top of the drying tank and a second temperature sensor which is located at the top of a charging barrel and used for measuring air temperature are set. According to the crystallization and drying system and method, the radioactive waste liquid in the charging barrel is kept in a non-boiling evaporation state at the saturation temperature, from vaporization, steam can be prevented from containing dirty liquid drops, the discharge requirement can be met on the premise that following processing facilities are not involved, and polluted devices are reduced.