<p indent="0mm">Considering the nonfatal engine faults (e.g., abnormal thrust) of a launch vehicle in the outer atmosphere flight phase, a method based on equilibrium flight theory for the evaluation of the vehicle’s orbit entry capability and continuous thrust guidance is proposed. First, the mechanism of mission failure caused by abnormal thrust fault is analyzed from the perspective of flight dynamics; on this basis, the simplified model of launch vehicle flight dynamics is established in the LVLH coordinate system, and the approximate analytical theory of equilibrium flight is provided. The conditions of an “equilibrium flight” and a “quasi-equilibrium flight” are further analyzed, and the differences between their guidance laws are compared. Next, the method and process of the online evaluation and decision-making of launch vehicles with an abnormal thrust are listed. Finally, numerical simulation is performed to reveal the relationship between thrust drop and orbit entry capability, as well as verify the correctness and practicability of the analytical theory of an equilibrium flight comprehensively. This simple and effective method integrates online capability evaluation and optimal orbit guidance, which can provide theoretical and technical support for rapid autonomous fault handling of launch vehicles with thrust faults.