In order to evaluate level of development of early metallurgical technology in Shandong Province, three slag samples unearthed from the Ying City relic site were analyzed by scanning electron microscope - energy - dispersive spectrometry ( SEM - EDS). The results showed that two samples are copper smelting slags and that one is an arsenic copper alloy melting slag, indicating the co-existence of two copper smelting processes. The results also indicated that the making of arsenic copper alloys was achieved by purposely adding As - containing minerals during the smelting operation. The copper minerals used probably came from the Beijiangshui copper mine while the arsenic minerals used came from the central mountainous area in Shandong Province. These slags should be dated to a period similar to that of the bronze artifacts unearthed from this site and are attributed to the Shang and Zhou Dynasties.