A method for making a life vest includes making first and second double-knitted fabrics from an artificial filament. Each of the first and second double-knitted fabrics includes inner and outer cloth layers. The first and second double-knitted fabrics are dyed. Then, the inner cloth layer of each of the first and second double-knitted fabrics is processed to form a brush structure on the inner cloth layer. The brush structure and the inner and outer layers of each of the first and second double-knitted fabrics undergo a heat-setting process so that the sizes of the brush structure and the inner and outer layers of each of the first and second double-knitted fabrics are stabilized. The first and second double-knitted fabrics are cut and sewn so that the outer cloth layers face outward and that the inner cloth layers face each other. A buoyant material is filled between a receiving space defined between the inner cloth layers.