The invention provides a low-temperature dyeing process of a fiber fabric. The low-temperature dyeing process comprises the processes of pretreatment, pre-sizing, dyeing, reduction clearing, fixing, softening treatment, drying, sizing, calendaring and rolling. In the dyeing process, the highest temperature does not exceed 100 DEG C, mild dyeing is carried out by using a gradual warming method and pH value regulation is carried out through a buffer solution, so that a proper acid environment required during the dyeing is satisfied and the dyeing effect is excellent; during the dyeing, a leveling agent is added to ensure that the dyeing is uniform; anhydrous sodium sulphate is added to postpone the dyeing process of the pigment and the temperature rises slowly at the same time, so that the uniform dyeing is ensured; a smoothing agent is added to prevent the scratching and local fibrillation; a penetrant and a diffusant are added to ensure that the penetration and the diffusion of the dyeing are relatively good; by means of the strict control in the aspects of temperature, acid, auxiliaries, time and the like, the low-temperature dyeing process of the fiber fabric has the advantages that the dyeing firmness is high, the dyeing is uniform, the dyeing stability is good and the effect is excellent at low temperature.