1. A decoration lamp for producing matched sound and illumination effects, the decoration lamp comprising: a decoration body having a front surface and a back surface; multiple fixtures mounted on the decoration body and respectively having: a first connector mounted on the front surface of the decoration body and having an opening; and a second connector mounted on the back surface of the decoration body and engaging with the first connector; multiple illumination units respectively mounted in the fixtures and exposed in the openings of the first connectors; a translucent cover mounted on the front surface of the decoration body to cover the illumination units; a speaker making different voices according to different sound signals; and a control device storing the sound signals, electrically connected to the illumination units and the speaker, and sequentially executing multiple modes, wherein each mode is applied to activate a part of the illumination units to form a certain pattern and to output one of the voices corresponding to the certain pattern by the speaker.