Hydrodynamics-based transfection is a kind of exogenous gene transfection. It’s a fast，convenient and high-level expression way. We injected a great deal of normal saline concluding the target gene into mice through caudal veins quickly，the exogenous gene could express highly in vivo. This way has already applied in animal models and gene therapy of liver-disease，myocarditis，nephropathy and anti-tumor. In addition，this way had widespread used in gene function，gene regulation，protein expression and gene therapy in vivo.