In response to the continuous advancement of oil and gas exploration, as well as the imperative to secure China’s energy supply, addressing the challenges of deep-earth resource extraction has become a crucial scientific and technological endeavor. Consequently, China has initiated two 10,000-m scientific and technological explorations of ultra-deep wells in the Tarim and Sichuan regions. This study aims to address the challenges associated with the effective deployment of acidizing working fluids under ultra-deep and high-temperature conditions. We developed a robust 200 °C-resistant weighted gelling acid system by optimizing the selection of weighting agents, corrosion inhibitors, and gelling agents. The system’s performance was evaluated in terms of rheological properties, high-temperature and high-pressure dynamic corrosion resistance, and other key metrics. The results demonstrate that the density of the weighted gelling acid system can reach up to 1.3 g/cm3. Additionally, at 200 °C, the system exhibits a high-temperature and high-pressure dynamic corrosion rate of less than 80 g/(m2 h). After 30 min of shearing at 170 s−1, the viscosity remains above 15 mPa s. These findings provide significant technical support for the successful application of acidizing fluids in ultra-deep, high-temperature reservoirs.