Heat dissipation assembly and electric device thereof

An electric device, suitable for installing an expansion card, comprising:

• a main board, comprising an expansion slot and a positioning column, the expansion slot accommodating the expansion card;
• a heat dissipation unit, provided on the expansion card, a first guide block being provided on a first side of the heat dissipation unit, and a first positioning component being provided on the first guide block;
• and
• a quick release hook, comprising a slide piece, a pressing component and a spring component, the slide piece comprising a buckle slot and a first oblong hole, the first positioning component penetrating the first oblong hole and being provided on the first guide block, such that the slide piece is arranged in the first guide block, the pressing component being protruding on the slide piece, the spring component comprising a first end and a second end, the first end being provided on the slide piece or the pressing component, and the second end extending from the first end to the first side,
• wherein the first guide block moves between a first position and a second position of the first oblong hole, the first guide block is located at the first position, the buckle slot abuts against the positioning column, the first guide block is located at the second position, and the second end of the spring component abuts against the first side.