The invention discloses an acid treatment agent for IGF-I chemiluminesent immunoassay, a sample pretreatment method, a kit and a detection method, and belongs to the technical field of in-vitro diagnosis detection. The acid treatment agent is mainly prepared from an organic acid solution with the concentration of 0.1-0.5mol/L and an inorganic acid solution with the concentration of 0.01-0.1mol/L or refers to an organic acid solution with the concentration of 0.3-2mol/L, and the pH value of the acid treatment agent is 1.5-3.5. After the acid treatment agent is mixed with a sample, the IGF-I and IGFBP in the sample can be well separated, and the detection requirement is achieved, so that the samples in low concentration range can be accurately and reliably detected. According to the IGF-I chemiluminesent immunoassay detection kit by adopting the acid treatment agent, the sample treatment method and the detection method, the samples in the low concentration range can be accurately and reliably detected.