Abstract: An auxiliary device to stick a film on a portable electronic product includes a holding base having plural sets of positioning holes and an auxiliary cover having one set of positioning posts. The positioning posts are inserted in the positioning holes to assemble the auxiliary cover and the holding base together and to tightly wrap the portable electronic product therein. The auxiliary cover has a limit frame which has four sides to form a hollow area within the limit frame. The hollow area corresponds to the screen or the rear cover of the portable electronic product. Through the present invention, a protective film can be stuck on the electronic product accurately, quickly and flat, without bubbles or wrinkles. By the same holding base to cooperate with different auxiliary covers, the present invention is adapted for electronic products in different sizes to save the cost and to enhance its convenience.