In order to realize the accurate simulation of concrete crack propagation, a two-dimensional concrete mesoscopic modeling method based on the geometric of actual aggregate is proposed. The method obtained actual aggregate geometric by image processing, and formed the random growth of actual aggregate through the random movement of aggregate contour points in the plane. In addition, the front polygons-rear circumcircle criteria was proposed, which simplified the conflict and overlap process between complex polygons. Using this method, threepoint bending beam tests were carried out to analyze the influence of aggregate shape on crack propagation and macroscopic properties. The results show that the larger the aggregate ovality is, the smaller the bending ultimate strength of the beam is, and the more obvious guiding and blocking effect is.