To investigate the flow characteristics and multi‑field coupling mechanisms inside the twin‑screw pump.Based on the Eulerian-Eulerian heterogeneous flow model and the immersed boundary method，a transient simulation of the flow field in a multiphase twin‑screw pump was conducted under varying gas volume fraction conditions.The variations in pump outlet flow rate，pressure，phase distribution，and rotor surface velocity were analyzed.The fluid pressure was applied to both the rotors and the liner to obtain the laws of radial，circumferential，axial deformation and stress-strain of the rotors and liner.Furthermore，the pressure at monitoring points was compared with experimental data，validating the accuracy of the results.The results indicate that the outlet flow rate initially increases and subsequently decreases with the rising gas volume fraction，reaching its maximum value at a gas volume fraction of 50%.The pressure exhibits a step‑like increase from the inlet to the outlet，remaining nearly constant within individual cavities.The gas volume fraction exhibits a positive correlation with the pressure‑boosting capacity of the last‑stage screw.The gas phase predominantly accumulates in the screw roots，near the outlet edges，and at the intermeshing zones of the screw rotors throughout the flow passage.The liquid phase exhibits relatively higher velocities at the outlet，the meshing region between the driving and driven screw rotors，and near the screw tips.The radial and circumferential deformations of the rotor reach their maximum at the outlet.Under a gas volume fraction of 95%，the maximum radial and circumferential deformations reach 3.501 7×10⁻⁶ m and 3.603 7×10⁻⁶ m，respectively.The radial deformation of the liner reaches its maximum at the outlet and exceeds the deformation values in all other directions.The structural strength of both the rotors and the liner meets the requirements under all gas volume fraction conditions.The gas volume fraction influences the pump's outlet flow rate，internal pressure distribution，gas‑phase distribution，liquid‑phase velocity，and structural deformations；however，it does not affect the structural strength of the rotors and the liner.This study can provide valuable insights for optimizing the geometric profile design of the rotors and clearance control of twin‑screw pumps，thereby effectively enhancing their transportation efficiency and operational stability under multiphase flow conditions.