Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein（CRISPR/Cas）is an adaptive immune defense system based on RNA for most bacteria and archaea.CRISPR/Cas technology modified from CRISPR/Cas system has become a strong genome editing tool，which has been widely applied in gene function analysis，gene modification and therapy.Other than being a strong genome editing tool，the “collateral cleavage” of type Ⅱ Cas has been employed as a rapid，inexpensive，and sensitive nucleic acid detection tool，exhibiting a great promise in nucleic acid molecular diagnosis.The representative research progresses in nucleic acid detection based on the type Ⅱ Cas are reviewed in this article，and an outlook on the application of CRISPR/Cas system in molecular diagnosis is proposed.