Abstract: Parabolic-trough solar thermal power, characterized by its green, low-carbon, and grid-friendly attributes, is a highly promising renewable energy generation technology. However, existing research lacks in-depth analysis of the dynamic response characteristics of the heat collection field and the steam generation system in the parabolic-trough solar thermal power plant. To address this gap, this study focuses on China’s operational 50 MW parabolic-trough solar thermal power plant in Delingha. A dynamic simulation model of the plant’s collector field and steam generation system was established on the domestic STAR-90 software platform and validated against the plant’s actual operational data. Subsequently, the dynamic responses under step perturbations of two critical parameters—Direct Normal Irradiance （DNI） and heat transfer oil flow rate—were investigated. Key findings reveal that when DNI fluctuates by ±50 W/m² around its design parameter of 900 W/m², the outlet temperature of the heat collection field exhibits a response time of 4 minutes and fluctuates within ±5.6 ℃; the steam generation system demonstrates a response time of 12.5 minutes for both main and reheat steam, with temperatures fluctuating by ±5.6 and ±4.0 ℃, respectively, and pressures varying by ±0.46 MPa （main steam） and ±0.07 MPa （reheat steam）. When the heat transfer oil flow rate of the steam generation system fluctuates by ±10% from its design value, the main and reheat steam exhibit response times of 8 minutes （for a step increase） or 9 minutes （for a step decrease）, with temperature fluctuations of ±0.4 and ±2.0 ℃, respectively, and pressure variations of ±0.4 and ±0.07 MPa.