A brushless motor assembling structure is used for being arranged on a motor body. The motor body comprises a stator and a rotating shaft. The rotating shaft passes through the stator. The brushless motor assembling structure comprises a positioning stand, a first circuit board and a second circuit board. The positioning stand is arranged on the stator, and has a through hole that allows the rotating shaft to pass through. The positioning stand is provided with a front side portion and a back side portion that are opposite to each other. The first circuit board is combined with the front side portion of the positioning stand, and is located between the positioning stand and the stator. The second circuit board is combined with the back side portion of the positioning stand. The positioning stand is located between the second circuit board and the first circuit board. Through the above design, the overall length of a motor can be reduced, and convenience is brought for dismounting and assembling of the circuit boards.