A quick assembly bicycle stem structure includes a front fork stem, a handlebar stem having a zigzag-shaped slot opening formed at a lower end thereof that is received in an upper section of the front fork stem, the zigzag-shaped slot opening including a first vertical slot and a second vertical slot that are spaced apart in relation to one another, a pin bolt coupled to the front fork stem and extending into the zigzag-shaped slot opening of the handlebar stem, the pin bolt configured to travel within the zigzag-shaped slot opening and to enter the second vertical slot from the first vertical slot when the front fork stem is rotated relative to the handlebar stem, and a nut assembly received over the handlebar stem and configured to threadedly engage the upper section of the front fork stem.