To improve the rapid response of a spacecraft and ensure that its trajectory-orbit unified design meets the requirements of speed, accuracy, and reliability, a rapid trajectory-orbit unified design method for spacecrafts was studied. First, the dynamic model of a spacecraft was constructed. The process and terminal constraints required for a spacecraft's trajectory-orbit unified design were analyzed and its flight procedure was given. Then, the traditional trajectory design numerical solution was improved. Through application of the improved Newtonian, Broyden rank-1, and steepest descent methods, the convergence of the methods was ensured when the initial value wad incorect. Finally, a multi-step and multi-layer method was considered, and the algorithm was further improved. The simulation result reveals that the proposed rapid trajectory-orbit unified design method for a spacecraft can be executed in 30 s, and the design orbital precision is 0.5 m. The algorithm is reliable, rapid, and accurate, and can be applied to trajectory-orbit unified designs of rapid-response spacecrafts.