Terahertz chip packaging systems impose stringent requirements on waveguide cavities in terms of miniaturization, high performance, and precision manufacturing. These demands pose significant challenges for the circuit design of the packaging cavity. Traditional design methods rely on manual modeling and parameter tuning, which are time-consuming and inefficient, and struggle to meet the needs of complex structures and multi-objective optimization. This paper proposes an efficient intelligent algorithm based on scripting interfaces of electromagnetic simulation software. The framework enables rapid modeling, performance simulation, and automated optimization of terahertz waveguide cavities. The effectiveness and feasibility of the proposed method are demonstrated through the design and optimization of a Y-band power amplifier cavity. The approach enables efficient and intelligent design of complex waveguide cavities for terahertz chip packaging and holds great promise for applications in high-speed communications, radar systems, and advanced packaging technologies.