In order to quantitatively evaluate and analyze the floating risk of the shield tunnel and carry out targeted risk control, the floating risk evaluation index system and evaluation standard of the segments of the shield tunnel on Huangpu Road Station-Xujiawang Station of Wuhan Metro Line No. 8 are constructed, and a floating risk evaluation model of the shield tunnel segments is established based on the cloud model and Dempster-Shafer(D-S) evidence theory. And then the subjection degree of the floating risk level of the monitoring section is calculated according to the engineering construction measurement data, the evidence is formed after naturalization, and D-S evidence fusion is carried out; the historical evidence is updated with the evidence at the present moment based on conditionization linear combination regulation, and the security risk level of the floating risk in the monitoring range is more secure at the present time. Finally, the corresponding treatment measures are given for the material factors with low security level. The results can provide a new idea and method for the evaluation and management of the floating risk of tunnel segments during construction.