A detection method for configuration of power supply units and a detection system using the same are provided. The detection method includes: storing a production information setting about configuration of power supply units in a field replace unit, in which the production information setting includes a number setting and a location setting; sensing actual configuration number and location of the power supply units by a sensing unit so as to obtain an actual configuration information; and reading the production information setting and the actual configuration information and comparing them by a controller, in which the controller determines that the detection is passed when the actual configuration information matches the number setting and the location setting; and the controller outputs an unusual message when the actual configuration information does not match the number setting and the location setting.