The invention relates to a lamp and a heat dissipation mechanism thereof. The heat dissipation mechanism is used for dissipating heat generated by lamp beads and comprises a substrate, heat dissipation pieces, connecting columns and insulating blocks; the substrate is composed of a substrate body and thermal conductive layers; the thermal conductive layers are arranged on the outer wall of the substrate body, and the lamp beads are arranged on the thermal conductive layers respectively; each connecting column has the thermal conductivity and is arranged between the substrate body and the corresponding heat dissipation piece; and each insulating block has the thermal conductivity and is arranged between the substrate body and the corresponding heat dissipation piece to enable insulation to exist between each thermal conductive layer and the corresponding heat dissipation piece. According to the lamp and the heat dissipation mechanism thereof, heat generated by the lamp beads sequentially passes through the thermal conductive layers, the connecting columns, the insulating blocks and the heat dissipation pieces, or the heat generated by the lamp beads sequentially passes through the thermal conductive layers, the connecting column, the insulating blocks, the connecting column and the heat dissipation pieces, so that the problem of lower thermal conduction efficiency of a car lamp is solved, and the service life of the car lamp can be prolonged.