The present invention discloses a wall clock with changeable size comprising a clock base, a front cover, a dial, a framework assembly, a rear cover and a framework assembly disposed between the dial and the rear cover, in which the framework assembly comprises a central dish for displaying time, which is configured to be suitable for passing through one of the holes of the dial; a plurality of arms, each of which is configured to be retractable in a length direction thereof, and has one end being secured to the central dish; and a plurality of fixing members for the arms, mounted removably and radially at different positions of the other end of the respective arms so that the framework assembly can be fixed in the clock base. By changing the length of the arms and the style of the dishes, variety in the function display and size of the assembled wall clock can be obtained, which not only increases the decorative function of the wall clock, but also decreases the mold and manufacturing cost, shortens the manufacturing and product development time.