The invention relates to a structure fixing a component on a printing circuit board and fixing method thereof. A thermosetting plastic precursor is printed between the printing circuit board and the component after the component is welded on the first surface of the printing circuit board by solder paste. When hot technology is performed on the second surface of the printing circuit board, the thermosetting plastic precursor is heated to polymerize into thermosetting plastic to fix the component on the printing circuit board. The polymerization temperature of the thermosetting plastic precursor is lower than the fusion temperature of the solder paste.