The invention provides a method and its kit for quantitatively detecting a specific analyte with a single capturing agent. The quantitative detection of a specific analyte with a single capturing agent comprises: firstly combining the tested analyte with a solid phase capturing agent, then labeling analyte which has been trapped by the capturing agent with a report molecule; secondly eluting the labeled analyte from the complex, recombining the tested analyte with a new solid phase capturing agent, and ascertaining the content of analyte by detecting the report molecule's label signal. The kit of the invention comprises a capturing device, a detecting device, a report molecule for labeling and an analysis substance eluate. The advantages of the invention are the need of one single capturing agent, the capability of detecting for many analytes which can't be tested at present, wide application, high sensibility and low noise. The invention can be applied to diagnosis, medical expertise, new medicine development, application of protein micro array and chip, and fundamental research.