The present invention relates to a heatsink and a heatsink-positioning system. The heatsink-positioning system comprises a heatsink and a positioning device. The heatsink comprises a circular top, a ring-shaped sidewall and a plurality of foot portions. The ring-shaped sidewall connects to the circular top and extends away from the circular top. The ring-shaped sidewall has at least one first positioning portion used for fixing the heatsink. The foot portions connect to the ring-shaped sidewall and extend away from the ring-shaped sidewall. Each foot portion has an opening. The positioning device has at least one second positioning portion corresponding to the first positioning portion and is used for fixing the first positioning portion. By utilizing the heatsink-positioning system of the invention, the problem of displacement of the heatsink can be improved.