Abstract: China Demonstration Fast Reactor (CDFR) was chosen for the reference core of ADS sub-critical fast reactor, mainly studying on the feasible of transmutation minor actinides from the spent fuel of PWR(U). The design of CDFR referred to the BN-800 which is on construction of Russia. In the sub-critical fast reactor core, the inner 7 subassemblies of CDFR were replaced with lead target subassembly, the control rod subassemblies were replaced with the subassemblies which contain MA and depleted uranium, and the radial blanket of CDFR were replaced with reflect subassembly. MCNPX and ORIGEN2 code were used in the calculation. The calculation and analysis show that the sub-critical fast reactor is feasible for transmutation of minor actinides and can remain sub-critical when it adds some MA, it is feasible to choose the CDFR for the sub-critical fast reactor research.