Abstract: A wearable electronic device includes a plurality of secondary spheres and a main sphere connected in series. The main sphere includes a lower cover, an upper cover, a threading pillar, a chip, and a wireless transmitting component. The lower cover has a first assembling space. The upper cover is disposed on the lower cover and covers the first assembling space. The upper cover has a second assembling space communicated with the first assembling space. The threading pillar is clamped between the lower cover and the upper cover and is located in the first assembling space and the second assembling space. Both of the chip and the wireless transmitting component are disposed in the first assembling space, and the wireless transmitting component is electrically connected to the chip. An assembling method of a wearable electronic device is also provided.