Purpose The application of traditional silicon strip detectors in space experiments often suffers from heat and power consumption limitations when a large area has to be instrumented. Recently, a scintillating fiber detector with SiPM readout was proposed and adopted by ground high-energy experiments. Its excellent performance in track measurement and mechanical flexibility makes it a prospective candidate for large-area tracking detectors in the next-generation space experiments. This paper mainly focuses on its performance in cosmic-ray charge measurement. Methods A fast Geant4 simulation for a single tracker module was developed and compared with the beam test results. The non-uniformity of the detector response was studied. Moreover, a full tracker simulation using a variety of typical cosmic ray nuclei was implemented. The performance of a fiber tracker with multiple layers was evaluated. Results and conclusion The comparison between the simulation results and the beam test data of protons and helium nuclei shows a good agreement. The non-uniformity study reveals the strong dependence of the detector signal on the position and inclination angle of the incident particles. Then, a corresponding correction algorithm was developed and applied in the following data analysis. The preliminary result shows that the charge measurement capability of the fiber tracker composed of 9 XY superlayers is comparable to that of the AMS-02 inner tracker, which consists of 7 layers of double-sided silicon micro-strip ladders. This paper discusses the feasibility of using fiber trackers to measure cosmic ray charges and provide a guide for the optimization of detector design.