Abstract2D layer‐structured nanomaterials have attracted much attention owing to their excellent optical, electrical, and magnetic properties. In this study, a novel 2D zirconium tritelluride (ZrTe3) nanosheet material is prepared. The nonlinear saturated absorption characteristics of the ZrTe3 nanosheets are studied using the double‐equilibrium detection method. The saturation intensity and modulation depth are 100.6 MW cm−2 and 3.3%, respectively. A saturable absorber (SA) based on ZrTe3 is used in a harmonic passive mode‐locking erbium‐doped fiber laser for the first time. The results show that when the pump power is 50 mW, mode‐locking with a fundamental frequency of 5.82 MHz is achieved. The pulse width, center wavelength, 3 dB bandwidth, and signal‐to‐noise ratio (SNR) are 1.44 ps, 1563.7 nm, 2.31 nm, and 76 dB, respectively. With an increase in pump power, a high repetition rate of 483.1 MHz, corresponding to the 83‐order harmonic mode‐locked, is obtained at a pump power of 310 mW. The pulse width, 3 dB optical spectral width, and SNR are 1.302 ps, 3.14 nm, and 67 dB, respectively. This reveals that ZrTe3 nanosheets are excellent photonic materials that can be used to generate high‐repetition‐rate pulse lasers and have great application potential in ultrafast photonics.