Abstract: An assay kit for in-situ hybridization (Rho GDP dissociation inhibitor beta, ISH) of RhoGDI2 gene, an assay method therefor and a use of the assay kit are provided. The assay kit includes: a hybridization probe, a marker, a hybridization solution, and an enhancement reagent. The hybridization probe has a sequence of SEQ ID NO. 1. The assay method includes steps of: (a) mixing the hybridization probe of the assay kit with a to-be-tested RNA on a substrate to form a hybridization complex; and (b) assaying the hybridization complex formed in the step (a). The use of the assay kit is applied the assay kit to prepare a therapeutic medicines for early metastasis of a carcinoma or a relapse disease. The assay kit of the present invention can enhance sensitivity and strengthen specificity. Meanwhile, the assay method of the present invention can increase operational convenience and simplify procedures, so that the assay method can be popularized in the medical institutions including local hospitals.