The invention discloses a replaceable fast mounting ceiling lamp which comprises a mounting rack, a base, a light source component, a lampshade and a plurality of locking fixing pieces, wherein two ends of the mounting rack are arranged on the base through the locking fixing pieces; the outer side parts of the locking fixing pieces protrude out of the outer side wall of the base; a plurality of buckling parts are arranged on the inner side wall of the lampshade; the locking fixing pieces protruding out of the outer side of the base are clamped in the buckling parts; the base and the lampshade are mutually enclosed to form an accommodating space; and the light source component is arranged in the accommodating space. According to the replaceable fast mounting ceiling lamp, through arranging the locking fixing pieces and the buckling parts, the base and the lampshade are simpler and more convenient to dismantle and mount and the replaceable ceiling lamps of different sizes can be conveniently replaced. In addition, the locking fixing pieces can lock and fix the mounting rack on the base, also can detachably connect the base and the lampshade, are multifunctional, are simple in structure, simple and convenient to operate and high in practicality and has higher significance.