Cadmium ions (Cd2+) are some of the major pollutants in oilfield chemicals. To reduce the pollution of oilfield chemicals, it is necessary to detect and control the content of Cd2+. In this study, we synthesized a highly sensitive and specific monoclonal antibody against Cd2+ with an IC50 of 1.97 ng mL-1 and no cross-reactivity. Based on this antibody, a colloidal gold immunoassay strip detection assay with an IC50 of 1 mg kg-1 and a detection range of 1.0-20 mg kg-1 in oilfield chemicals was developed. This assay could be completed in 20 min and can be used for Cd2+ on-site testing in oilfield chemicals and improve supervision efficiency in oil exploration and development.