The gas-solid micro-fluidized bed reaction analyzer (MFBRA) has been successfully applied to the analysis of reaction kinetics because of its isothermal differential characteristics. However, its application is limited to normal pressure conditions at present, and its applications under pressurized conditions are not established yet. Micro-fluidized bed (MFB) is the core part of an MFBRA. It is of great significance to investigate the behavior of the pulsed feeding gas injection in an MFB under high temperature and high pressure conditions by computational fluid dynamics. It is in gread need to reveal the disturbance of the pulsed feeding gas to the bed material fluidization, deepen the theoretical understanding and provide guidance for the usage, and optimization of a pressurized MFB. In this work, a three-dimensional simulation was performed to simulate the pulsed feeding gas injection into an MFB under high temperature pressurized conditions, and to improve the structure of the feeding tube. The fluidization inside the MFB was described by two-fluid method (TFM). It was confirmed that the model adopted here captured the pressure drop inside an MFB, agreed with experimental data. It was found that temperature and pressure had opposite effects on the fluidized bed disturbance caused by the pulsed feeding gas. Increasing the pressure could enlarge the disturbance of the feeding gas to bed fluidization because the kinetic energy of the feeding gas increased, while increasing the temperature could reduce the fluidized bed disturbance. By expanding the feeding tube in axial and radial direction, the decreasing effect of gas velocity caused by tube expansion could be stronger than the increasing effect of gas velocity caused by the non-slip wall condition. Therefore, the terminal velocity of the feeding gas decreased, and its disturbance to the bed could be weakened. Compared with radial expansion, axial expansion was more effective to weaken the disturbance and should be the main method for improving the structure of the feeding tube.