In order to investigate concrete cracking characteristics, the traditional average method was modified based on meso-mechanics theory and used in cracking zones. Using different average methods, concrete specimens with different sizes but the same grading and size distributions were analyzed, and cracking characteristics and mechanisms of cracking size dependency were studied. The results show that cracking stress-strain curves obtained with the cracking zone average method are size independent, and they can represent the entire cracking process and determine important cracking parameters. It is also shown that when the specimen size varies, the area and mechanical characteristics of local nonlinear cracking zones are barely affected by the specimens size change, while the area and mechanical characteristics of linear elastic zones are highly affected by the specimens size change, making the global average mechanical characteristics change a lot, thus the cracking size dependency occurs.