Abstract: The disclosure provides a kit for detecting microsatellite instability and a method therefor. The kit includes a negative control, a plurality of qPCR reaction solutions, a qPCR premix and a sterile enzyme-free water; the plurality of qPCR reaction solutions includes 6 pairs of upstream primers and downstream primers of which the MSI mutation site is amplified, and a reference probe for the internal reference and a detection probe for the mutation site. The difference between the amplification of the gene and the gene at the mutation site of the samples and the negative control is used to detect the microsatellite instability. The method and kit as provided is easy and simple without the need of normal tissues being a control, and the need to open the cap. By doing so, aerosol pollution is avoided and sample supplies are conserved.