Fe3O4 nanoparticles (Fe3O4-NPs) are outstanding magnetic materials, which have plenty of applications in many fields, such as magnetic detection, ultrafast photonics, optical communication, etc. In this paper, we used co-precipitation method to synthesize Fe3O4-NPs, which formed saturable absorber (SA) in our erbium-doped fiber laser (EDFL). We obtained stable Q-switched pulses with central wavelength of 1530.46 nm and signal-to-noise ratio (SNR) of 54.4 dB when the pump power was 400 mW. When the pump power increased gradually, outline of the spectrum changed little, however, the repetition rate (RPR) increased gradually, meanwhile the pulse duration decreased gradually. In this experiment, when the pump power reached its maximum of 415.4 mW, the RPR reached its maximum of 72 kHz, meanwhile the pulse duration reached its minimum of 2.44 μs. It shows that Fe3O4-NPs-based passively Q-switched EDFLs have many potential applications, such as laser frequency doubling, laser radar, and study of interaction between light and matter, etc. © 2022 Elsevier Inc.