Provided are a four-pole brushless direct current position motor and a detection method thereof. In a brushless direct current motor control system, a Hall sensor is small in size, difficult to install and large in output signals errors. A photoelectric encoder cannot be applied to poor environments which are severe in vibration, damp and have oil stain and dust. The four-pole brushless direct current position motor comprises a casing (3), the top of the casing is provided with an end cover (8), a circuit board (7) is installed on the lower surface of the end cover, the position of a lower opening of the casing penetrates a solid shaft (1), a bearing (2) is installed between the inner surface of the casing and the solid shaft, the upper end of the solid shaft is sleeved with four-pole annular magnetic steel (4), the outer portion of the four-pole annular magnetic steel is sleeved with an annular iron core (5), a switch Hall sensor (6) is installed between the four-pole annular magnetic steel and the annular iron core, and a power supply circuit (9) is integrated on the circuit board and connected with the switch Hall sensor. The four-pole brushless direct current position motor is used for brushless direct current motor phase-change position detection.