Abstract: To address the challenge of identifying weak signals under low wellbore flow conditions with existing distributed acoustic sensing (DAS) methods based on upstream and downstream acoustic signal distributions, an active thermal excitation technique was introduced to enhance signal contrast. To verify the feasibility of the proposed method, a full-scale indoor experimental setup was established for physical simulations, and numerical simulations were performed. Both physical simulation experiments and numerical simulations demonstrate that active thermal excitation significantly enhances the low-frequency DAS signal response. Stable signals can be obtained when the optical fiber is in direct contact with the heated section. The signal intensity is primarily governed by the thermal excitation strength. A thermal excitation intensity of 10 °C is sufficient to generate clear and distinguishable signal edges, meeting engineering application requirements. When the flow velocity is equal to or greater than 0.0666 m/s, corresponding to a flow rate of 24 m³/d, the error of the peak tracking method remains within 10%. However, the feature points shift due to sufficient heat exchange at low flow velocities, requiring further algorithm optimization. The numerical simulation results show good agreement with the experimental data in terms of response trends and flow velocity calculations. and the structural similarity index further confirms the validity of the numerical model. The study indicates that employing a thermal excitation intensity of 10 °C combined with the peak tracking method reduces system energy consumption while ensuring calculation accuracy. The active thermal excitation provides a novel solution for downhole flow monitoring in low-productivity wells. Nevertheless, this method is only applicable to the working conditions with flow rates equal to or greater than 24 m³/d. Future work should focus on optimizing the feature recognition algorithm under low flow rate conditions and validating its adaptability to field conditions.