The present disclosure discloses a lamp holder, a battery assembly and a supplementary lighting lamp. The lamp holder includes a housing and a rotation assembly rotating relative to the housing, wherein the rotation assembly includes a cover body, a resisting member and an adjusting member moving relative to the cover body, and the housing includes a fastener formed on a first end thereof. The adjusting member moves on the cover body so that the resisting member is resisted against the fastener, thus the rotation assembly is clamped with the housing or separated from the housing. The present disclosure has the advantages of convenient disassembly and good waterproof performance.