The invention relates to a conductive elastic fiber and a preparation method thereof. The preparation method comprises the step of carrying out composite spinning on thermoplastic polyether ester containing conductive filler or thermoplastic polyurethane containing the conductive filler and thermoplastic polyether ester or thermoplastic polyurethane, thus obtaining a conductive elastic fiber is obtained. In the composite spinning process, the melt viscosity ratio of the two components is (1-1.5):1, and the weight ratio of the two components is 10:90 to 90:10. The prepared product has macroscopic self-crimping elasticity and intrinsic entropic elasticity at the same time, the volume resistivity of the product is 1*10<-2>-1.5*10<6> omega.cm, the elongation at break of the product is 100-1000%, the elastic recovery ratio of the product is more than or equal to 95%, the crimp percentage of macroscopic self-crimping of the product is 50-500%, and the deformation range of intrinsic entropicelastic deformation is 20-100%. The prepared product has high product elasticity, high stability and large strain response range, the preparation technology is simple, the cost is low, and the economic benefit is good.