Abstract: To ensure the anti-crack performance of reinforced concrete raft foundations that can meet structural durability，anti-leakage and appearance of basements，it is necessary to check and control the maximum width of crack according to relative technical codes． In structural design right now，for these raft foundations which were allowed in use with controlled cracks，it was mainly the reason that cracked raft foundation cannot be used normally because thermal post-cast band was selected on the whole only depending on experience，and less calculation checking was taken for the maximum width of crack under the most unfavorable case，or wrong checking case was chosen in design． Based on technical analysis and practical design review for the raft foundation in basements，some concerned problems were studied and discussed，such as combination concrete tensile stress，reaction force of raft underside from groundwater buoyancy，acceptable maximum crack width，efficiency of post-cast band．