The invention provides a method for communicating region in a scan unite image and a device thereof. The method includes steps as follows: firstly, scanning present line of the image for obtaining a communication segment of the present line; secondly, taking out a communication segment as the present segment for processing communication analysis; thirdly, judging upper line whether having a communication segment communicated with the present segment, if yes, executing fifth step, if no, executing fourth step; fourthly, distributing target sequence number for the present segment, and storing the position information of the present segment to a structure body corresponding to the target sequence number; fifthly, confirming a first communication segment, uniting the present segment and each non-first communication segment into the first communication segment, and releasing the structure body stored the non-first communication segment. The method can complete unite only needing once scanning, needs not be distributed overfull temporary data cache which can solve technique problem that the prior technique is not suitable for operating in a hardware environment.