Abstract: The immobilization formulation of cement mortar for the super-compressed pies in the boxes was studied, which are the retrieval intermediate and low level radioactive solid waste after super compressed. The immobilization formulation can meet the requirements of safe transportation, storage and disposal, and ensure to be used in engineering. By investigating the factors, including water cement ratio, cement sand ratio, sand size distribution and the additives amount, on the characterization of cement mortar, such as the fluidity, the setting time, the temperature rise and the performances of the solidified bodies, the immobilization formulation meet the nuclear industry standard (EJ1186-2005), and is suitable for the existing engineering device. The formulation includs 0.450∶1 water cement ratio, 1∶1.6 cement sand ratio, 1∶2∶1 sand size distribution and 1‰ （mass fraction） the retarder.