A display apparatus and an image data processing method thereof are provided. The display apparatus includes a first display panel, a second display panel and a backlight module. The image processing method includes: receiving image data; detecting an ambient temperature and an ambient brightness to obtain a detection result; when the ambient temperature is lower than a preset temperature value, selecting the image data to be divided into a plurality block data by display location or gray level range according to the ambient brightness, and performing a blur process on the block data to generate adjusted image data; when the ambient temperature is not lower than the preset temperature value, performing a binary process on the image data to generate the adjusted image data; and driving the second display panel according to the adjust image data.