Flyback converter is the best choice for the low power DC-to-DC switching mode power supply in modern industry. Both low cost and simple circuit structure are enough to explain its great popularity. This thesis is based on the topology of Flyback converter, the control integrated circuit UC3844 as a pulse width modulation has been employed to set up one 24 watts low power Flyback converter model. In simulation, utilize the help of EDA software, namely PowerSim, to be done in order to simulate the circuit. With the design of circuit, probe into the influence degree to the circuit of Power Factor, Total Harmonic Distortion, Ripple Factor, Output Voltage, Snubber Circuit, Start Up Circuit, Filter and Load Impedance in the design process. Finally, looks forward to a reference of design for the engineers who want to design Flyback converter and a help while developing the new products in the future.