An on-going research project is to develop a micromachine driven actively and wirelessly by external magnetic field. The micromachine has great potential for being used in medical fields such as gastrointestinal endoscopy. The ultimate goal is to develop a control mechanism capable of moving the wireless endoscope through the human's gastrointestinal tract in any direction with minimum level of harm to human body. This paper establishes fluid dynamics model suitable for micromachine's movement in intestinal tract, simulates pressure distributions of micromachine's surface, and further calculates driving and load torques. Based on the fluid simulation results, parameters for generating appropriate rotating magnetic field can be calculated. This fluid dynamics simulation method provides a novel approach to analyze biomedical micromachine's mechanical properties under external electromagnetic equipment.