The spin Hall effect of light (SHEL) can be observed by the dark strip resulting from weak measurement. We find that the SHEL of a partially coherent beam (PCB) has a similar phenomenon as well. However, the dark strip in the SHEL of a PCB cannot be explained by considering the beam as an assemblance of coherent speckles. Also, the dark strip in a PCB is not purely dark. By analyzing the autocorrelation, we show that the SHEL of a PCB is the result of overlapping coherent speckles SHEL. We further prove our conclusion by adjusting convergence and incident angles. Finally, we develop a qualitative theory to clarify the SHEL of a PCB.