In this paper, an auto-tuning AR (area ratio) ejector and an auto-tuning NXP (nozzle exit position) ejector are designed to solve the contradictions between the fixed structure and the dynamic primary pressure driven by multi-condition low-grade heat energy. A CFD (Computational Fluid Dynamics) model is used to calculate the performance of the ejector under different operational conditions. The effects of both AR and NXP on the performance of the ejector are systematically studied. The optimal area ratio increases linearly along with the primary pressure, and the optimum NXP decreases as the primary flow pressure increases. Following this, auto-tuning AR and NXP ejectors are designed to enhance the performance of the ejector by self-adjusting the AR and NXP with a variation in primary flow pressure. Simulation results show that the auto-tuning ejector has a strong ability to improve the ejector performance compared with the constant structure ejector.