The utility model discloses an overcritical CO2 pipeline unloading experimental apparatus based on multistage throttle, including trunk line and trunk line vertically throttle pipeline section two parts, the entry and the CO2 source intercommunication of trunk line, and install the control valve at the entry, installing differential pressure sensor and temperature sensor on the trunk line, outlet controlled valves is installed in the trunk line export, and outlet controlled valves's export links to each other with the throttle pipeline section, the throttle pipeline section install control by throttling valve, temperature sensor and pressure sensor for gather throttle back temperature and pressure.