The invention discloses a shower arm capable of being directly locked through a coin and locking method of the shower arm. The shower arm comprises a water inlet body, a rotating pipe and an inner core assembly for being connected with and locking the rotating pipe. The shower arm is characterized in that a locking nut locked with the thread section of the inner core assembly is arranged in the rotating pipe; the outer end face of the locking nut is provided with a locking groove, wherein the coin can be directly clamped into the locking groove to rotate the locking nut to lock the rotating pipe; the space size of the peripheral wall of the locking nut is smaller than that of the inner wall of the rotating pipe; the locking nut can be freely rotated in the rotating pipe to be locked or loosened in the rotating pipe. After the shower arm is used for a period of time, the rotating pipe is loosened, the coin is used to be directly clamped into the locking groove in the outer end face of the locking nut in the rotating pipe, and the coin is rotated to drive the locking nut to adjust and lock the rotating pipe again. A user can directly use the coin to adjust the rotating pipe so as to adjust the torque and does not need to use a special tool. The rotating pipe can be directly adjusted and locked again without disassembling an end cover. The shower arm is easy and convenient to use and unlikely to be loosened.