Controlling Method for Fixing a Scale Ratio of Browsing Image of Touch Device

A controlling method for fixing a scale ratio of browsing images of a touch device, which performs a displaying area control of a browsing image shown on a display screen, the controlling method comprises the steps of:

• (a) determining a zooming region on a display screen, which is determined by pinching the browsing image from a selected position to thus zoom in or zoom out the browsing image, and the scale ratio of zooming is accordingly determined;
• (b) displaying a screen-locking icon on the display screen, wherein the scale ratio is locked when the screen-locking icon is triggered to be in a locking state;
• and
• (c) displaying the other browsing images with the same scale ratio of zooming and with a viewing size same as the zooming region.