Abstract: The anticancer rare sugar D-allose was converted from D-psicose by E. coli BL21/ p ET-22b-tl-rpib.The LC-MS/MS results showed that 25% of D-psicose was converted to D-allose in the reaction product mixture. The p I of the recombinant protein was 6.3 determined by isoelectrofocusing and was successfully applied in isoelectric precipitation. The methods of separation and purification of D-allose was established according to DTF-Ca2 +cation exchange chromatography with a flow rate of 1m L/min, column temperature at60℃ and the loading volume of 4m L.