The invention discloses a shield segment connecting screw bolt stress state detection method and relates to the crossing field of tunnel engineering on-site monitoring and construction technologies. The method comprises the following steps: in shield segment assembling processes, all shield segments are connected via connecting screw bolts on which strain sensor assemblies are mounted; the connecting screw bolts are enabled to serve as devices for detecting on-site stress on connecting seams among the shield segments; in shield construction or operation processes, the strain sensor assemblies in the connecting screw bolts are used for measuring multiple strain values of the screw bolts in real time, stress states of the screw bolts are analyzed according to the multiple strain values that are measured in real time, and therefore mechanical properties of the connecting seams among the shield segments can be monitored on site. The method disclosed in the invention can be used for accurately, quantitatively and scientifically evaluating mechanical behaviors of the connecting screw bolts of the segments and visually reflecting stress changes of the connecting screw bolts, a high automation level and simple operation can be realized, a small number of auxiliary devices are required, and the method is suitable for tunnel construction or scientific research data collection.