High entropy alloys (HEAs) formed with simple crystal structures such as FCC and BCC have been reported exhibiting superior tensile or compressive properties, resistance to wear, high thermal stability. However, few works were carried out on the wettability of the molten metals on HEAs substrate. And the general objective of this work is to better understand the wettability of the molten metals on the HEAs substrate. Bi-Sn alloy with the low melting point and the AlCoFeNiCr HEA and the CuCoFeNiCr HEA were selected as experiential materials. By the sessile drop method, the wetting behavior and the interfacial characteristics of the molten Bi-Sn on the AlCoFeNiCr HEA and the CuCoFeNiCr HEA substrate were investigated. The scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS) was used to analyze the microstructure the Bi-Sn/AlCoFeNiCr HEA and Bi-Sn/CuCoFeNiCr HEA interface. The results show that the AlCoFeNiCr HEA and the CuCoFeNiCrHEA form with a single solid solution structure. However, Bi-Sn molten alloy on CuCoFeNiCr HEA substrate has better wetting characteristics than Bi-Sn molten alloy on AlCoFeNiCr HEA substrate. With increasing wetting temperature, a number of intermetallic compounds existed at the interface between the molten Bi-Sn and the CuCoFeNiCr HEA substrate, and the diffusion of Sn atom along the Cu-rich solid-solution phase in CuCoFeNiCr HEA is much more intense. On the contrary, interface of the Bi-Sn/AlCoFeNiCr HEA system is still the straight interface, and there are new intermetallic compounds on the Bi-Sn/AlCoFeNiCr HEA interface with increasing wetting temperature. It is found that the Cu-rich phase in CuCoFeNiCrHEA provides a “wetting channel” for the wetting process between the molten Sn and CuCoNiFeCr HEA substrate, which result in the two wetting systems with different wetting mechanism.