Jet-wake flow and secondary flows are undesirable in torque converters as they are responsible for flow losses and flow nonuniformity; that is, jet-wake flow and secondary flows negatively affect the torque converter performance. Therefore, it is very important to investigate and minimize the undesirable flows to decrease flow losses in torque converter. However, the existing studies are limited to employ geometry design parameter modifications rather than focusing on the actual causes and intrinsic physical mechanism that generate the flows to reduce the flow losses. In this paper, Calculation model of a torque converter is presented first and a three dimensional CFD code was used to simulate the internal flow field of a torque converter. The simulation results coincide with experimental measurements, which verifies the validity of the method. Based on flow field calculation results, the internal flow field of impeller, turbine and stator were analyzed, respectively. The rothalpy distributions of three elements were also investigated to analyze the magnitude and location of the loss occurring in the flow passage. To provide the designer with a more fundamental understanding of how the flows behave, a study on the formation mechanisms of jet-wake flow and secondary flows in a torque converter is proposed. A model based on the vorticity equation for a rotating system was derived to investigate the actual causes that generate vortex secondary flows. It can be employed to accurately predict secondary flow trends and early in the design process to optimize element flow shapes that intrinsically reduce secondary flows.