Natural gas flooding is a crucial technique for enhancing oil recovery and helpful for the efficiency utilization of energy, where throttling nozzles serve as essential components within the injection and production systems. However, most existing throttling nozzles are designed with fixed structures, making it challenging to adjust flow rates and pressure drops online. It proposes a novel adjustable downhole multi-hole throttling device that allows for the regulation of nozzle loss characteristics by adjusting the number of flow-through holes online. The SST k-ω turbulence model and the NIST physical property model were used to simulate the flow of supercritical mixed fluids within the nozzle, obtaining the flow field distribution characteristics inside the throttling device and analyzing the throttling behavior of the nozzle under different operating conditions. The results show that a non-uniform distribution of the flow rate between the nozzle channels was observed, and there is an asymmetric distribution characteristic of the flow field in the nozzles. Besides, the velocity in a single nozzle channel shows a rapid increase and then a decrease, and the pressure shows a rapid decrease and then a slight increase. The pressure drop across the gas nozzles was analyzed under different injection flow rates and varying numbers of holes. Under a pressure drop of 4 MPa, the device can achieve flow regulation over a wide range from 1.5×10⁴ to 1×10⁵ m³/d under standard conditions. A pressure drop prediction equation was established based on the simulation results, enabling quick prediction of gas nozzle pressure drops according to desired flow rates. Thus, it provides guidance for application of the new nozzle, enhancing oil production efficiency, extending the life of oil fields and achieving sustainable development of energy.