Abstract: The distribution of mass in the spontaneous fission of 252Cf was investigated by the radiochemical determination of the absolute fission yield for 35 mass chains. A summation of the mass-yield curve gives a value of 199.4% which is in very good agreement with the value of 200 % in fission. The mean masses of the light and heavy group are located at 106.39 and 141.82 respectively. The average of neutron number per fission (v) is 3.79±0.12. The peak-to-valley ratio is≥370.