We theoretically investigate a Dy3+-doped chalcogenide fiber lasers operating at 4.3 μ m based on the rate equations and propagation equations. The two main pump bands for 1319 and 1707 nm corresponding to the 6H15/2→6H9/2 and 6H15/2→6H13/2 transitions are discussed in detail. The predicted maximum slope efficiencies are determined to be ~7.8% and ~15.1% for the two pumping wavelength, respectively. Besides, the variety of laser performance has been systematically analyzed when the pump configurations, fiber length, fiber loss are varied. This numerical analysis might be useful to explore the 4.3 μm lasing operation for the mid-infrared chalcogenide fiber lasers in future.