A circuit board heat dissipation system includes circuit board unit that includes a motherboard and a daughterboard, a base seat, and a fastening unit that includes a plurality of first and second fastening components. Each first fastening component extends through the daughterboard and is engaged with the base seat. Each second fastening component includes a long fastener that extends through the base seat and the daughterboard and that is engaged with the motherboard, and a flat washer and a resilient member that are sleeved on the long fastener. The resilient member is disposed between a head portion of the long fastener and the flat washer for biasing the base seat and the daughterboard against the motherboard.