In this paper a new approach of obtaining the electrical properties of the power lateral double-diffused metal-oxide-semiconductor field-effect transistors (LDMOSFET) is proposed. The device is regarded as a junction field-effect transistor (JFET), the N-well region, in series with an active metal-oxide-semiconductor field-effect transistors (MOSFET). The I-V relation of these two parasitic FETs were first separately obtained from actual device structure and then combined together to generate the I-V relation for the power MOSFET. This model also explains why the transconductance has a maximum value at intermediate gate voltage and decreases drastically with higher gate voltages. The simulation program, MEDICI, verifies the accuracy of this analytical method. Since the model contains only two parasitic devices, it affords a first and easy method to analyze the I-V characteristic of power MOSFET.