The invention relates to a cellulose fiber cationic modification process, belonging to the technical field of textile dyeing. The cellulose fiber modification process comprises the following steps: putting cellulose fibers in a container, then adding water to the container, and then carrying out modification treatment on the cellulose fibers with two kinds of cationic modifiers, namely low molecular quaternary ammonium salt cationic modifiers and a high molecular quaternary ammonium salt cationic modifier, thereby obtaining modified cellulose fibers after modification treatment is completed, wherein the low molecular quaternary ammonium salt cationic modifiers are epoxy quaternary ammonium salt compounds; the high molecular quaternary ammonium salt cationic modifier is branched polyepichlorohydrin dimethylamine. The cellulose fiber cationic modification process has the beneficial technical effects that the two kinds of specific modifiers are adopted and the synergistic effects of the modifiers are given play to, so that the modified cellulose fibers achieve salt-free low-alkali dyeing in subsequent dyeing, have the effects of reducing pollution, saving the cost, simplifying the process and reducing the difficulty, have good modification and subsequent dyeing effects, and are suitable for large-scale industrial production.