Abstract: A lamp structure is provided in which a roof rack fixed on top of a car has an engaging slot for locking with a detent portion formed on the bottom of a positioning unit. A connecting portion extending on the detent portion has a fitting indentation with a positioning member penetrating therethrough, one end of the positioning member having a snap-fit portion provided on one end and a positioning pulling lever pivotally provided on the other end. A warning lamp having a snap-fit groove for engaging with the snap-fit portion is combined with the connecting portion. Therefore, the warning lamp has higher assembly position so that light emitted from the warning light is clearly visible by rear drivers from a longer distance and hence has better eye-catching and warning effect, and better driving safety can be achieved.