The invention relates to a cellulosic fiber fabric reactive dye salt-free deep-color dyeing method, which comprises the following steps: (1) preparing a modifier aqueous solution, increasing the temperature to 60-80 DEG C, adding a test sample, stirring, adding sodium hydroxide, stirring, washing and drying to obtain a modifier test sample; and (2) adding a reactive dye and a levelling agent, increasing the temperature to 60-80 DEG C, adding the modifier test sample, dyeing for 20-30 minutes in a stirring manner, adding substitution alkali, dyeing for 30-45 minutes in a stirring and thermal insulation manner, decreasing the temperature to the room temperature, soaping, washing and oven drying. According to the invention, the modifier is used for modifying cellulosic fibers, so that the repulsive force between dye anions and fibers can be reduced, the purpose of fabric reactive dye salt-free dyeing can be achieved, the method is simple and convenient to operate, the effect is obvious, no additional equipment is required, and the cost is controllable.