Synthesis of 6,6’-diamino-6,6’-dideoxy-alpha,alpha-D-trehalose, the polyaddition with diisocyanates, and the characteristics of the resulting synthetic carbohydrate polymers have been disclosed. Among four preparative approaches to efficient preparation of diaminotrehalose starting from trehalose, that involving first protection of the C-6,6’ hydroxyl groups with trityl groups, acetylation of the remaining hydroxyl groups, detritylation, tosylation, azidation, deacetylation, and finally catalytic reduction proved to be superior to the others, and the overall yield was as high as 26%. The resulting diaminotrehalose was subjected to polyaddition with diisocyanates to give polyureas containing trehalose residues in the main chain. The polyureas showed high solubility in organic solvents. The derived membranes were evaluated in dialysis with urea and vitamin B-12 and exhibited marked permeability. The polyureas were also susceptible to trehalase and alpha-amylase, suggesting the high potential as a novel type of biodegradable synthetic carbohydrate polymers.