A light source assembly comprises a fixing assembly, light sources, reflectors, a fixing plate and a locking mechanism. The fixing assembly comprises a first fixing end, a second fixing end and two opposite installing faces, the first fixing end and the second fixing end are arranged oppositely, the installing faces are arranged between the first fixing end and the second fixing end, and the light sources are arranged on the two installing faces in a one-to-one corresponding mode. Two reflectors are arranged on two sides of the fixing assembly oppositely, reflecting sides of the reflectors face the light sources, the reflecting sides and the installing faces define accommodating cavities with emergent light openings, each light source is accommodated in a corresponding accommodating cavity, and emergent light directions of the emergent light openings are parallel to the installing faces. The fixing plate comprises a load bearing face and a clamping portion. The clamping portion is fixed on the load bearing face and clamped with the first fixing end, and the locking mechanism is fixed on the load bearing face and comprises a telescopic piece. When the telescopic piece is stretched, the telescopic piece is clamped on the second fixing end, and when the telescopic piece is retracted, the second fixing end is released. The fixing assembly can be clamped or released through stretching and retracting of the locking mechanism, and light source installing and detaching are simplified. In addition, a lamp comprising the light source assembly is further provided.