The structure of concrete material size effect is a key issue to extrapolate laboratory measurements applied to predict the actual cumulative damage of engineering structures damaged.This project required concrete with different size of aggregate to confined experiment,observing the micro-cracks' evolution characteristics of the sample.The main task is to discuss the impact of the laws about the crack propagation of the confined aggregate materials of concrete specimens.Experimental results shows that the aggregate sample size is large and less wide surface cracks,aggregate size becomes smaller,thin and produce more small cracks.