Detection methods for an electroplating process are provided. A detection method includes immersing a substrate into an electrolyte solution to perform an electroplating process. The electrolyte solution includes an additive agent. The detection method also includes immersing a detection device into the electrolyte solution. The detection method further includes applying a first alternating current (AC) voltage or direct current (DC) voltage to the detection device to detect the concentration of the additive agent. In addition, the detection method includes applying a combination of a second AC voltage and a second DC voltage to the detection device to inspect the electrolyte solution. An impurity is detected in the electrolyte solution. The detection method also includes replacing the electrolyte solution containing the impurity with another electrolyte solution.