Weak signal studies can provide decision-making support to the strategic foresight process and strategy making, and have gradually become research hotspots. To find out the developmental trajectory of weak signal studies, an intermediacy network is constructed here after collecting scientific publications from the Scopus database with the time spanning from 1975 to 2020. Different from main path analysis, more details are illustrated in the intermediacy network, from which four developmental stages can be observed. Our preliminary research indicates that the intermediacy can serve as an alternative to main path analysis on discovering developmental trajectory.