A power chamber of a lighting fixture includes a chamber body receiving at least one power module. One of the power module and the chamber body includes a first fixing plate defining a sliding groove sunken inwards from a surface of the first fixing plate. The other one of the power module and the chamber body includes a fastener whose end is matched with the sliding groove. The power module and the chamber body are connected together through the fastener which is inserted into the sliding groove, therefore simple to assemble and disassemble. The power chamber can be a profile structure with low manufacturing costs. Power chamber cover(s) can be arranged on the side of the lighting fixture and can be integrally molded with pipes used for fixing the light source module.