Both shrinkage experiments of full-grade concrete and sieved concrete were conducted. The shrinkage mechanism of concrete was analyzed and a model based on the theory of elastic mechanics was built which can consider the influence of aggregate size and content. The relationships among concrete shrinkage deformation and elastic modulus of aggregate and cement pasted were analyzed, and the relation between the shrinkage deformation of full-grade and sieved concrete and experimental age was analyzed considering the influence of specimen size to concrete shrinkage. It is shown that the ratios of full-grade concrete to sieved concrete shrinkage increase with age increase, and the ratio at 180 age is about 0.29.