The operational mode of an interconnected large power grid is complex and changeable. Asynchronous acquisition of wide-area steady-state measurement will lead to measurement errors. An entire network simultaneous section generation technology based on a unified clock is proposed to improve the simultaneity of steady-state measurement. First, based on time-series characteristics of wide-area steady-state measurement, a method for data storing and updating circularly at fixed intervals is proposed to solve the problem of misalignment of section data. Then, the key nodes are identified by the electric ‘betweenness’ method. Based on the real-time requirement of key nodes measurement, unrefreshed measurements are modified by the spatio-temporal correlation characteristics. The timeliness and accuracy of the entire network simultaneous section are guaranteed. Finally, the simulation results based on a standard test system and a real power grid verify the correctness and effectiveness of the proposed method.