A producing technique of a soft jean is characterized by weaving jean grey cloth with twill by using chaine containing 20-90145603500f cotton, 10-8026240320f synthesized chopped fiber with a low contraction percentage of 2-2.5, and synthesized chopped fiber with a high contraction percentage of 5-6, and weft containing 20-901f cotton and 10-80516027304f synthesized chopped fiber; desizing the jean grey cloth; rinsing the jean grey cloth using water and drying same; spraying a mixed liquid containing an organosilicon surfactant and water into the jean grey cloth; performing warp direction preshrinking treatment of the jean grey cloth. The jean is softened by using an organosilicon surfactant combined with a biological enzyme, and is treated by an organosilicon surfactant and water after desized. Stiffening and cockle elasticity of the jean turn smaller, and content of non-fabric matter is less than 0.5%.