A numerical test code named RFPA (Realistic Failure Process Analysis) was used to investigate the stress filed transformation process of the reinforced concrete specimen under uniaxial tensile loading. The periodically distributed fracture spacing phenomenon exists in the reinforced concrete structure and the concrete cover thickness was an important factor influence the average crack spacing and crack number. The numerical simulation results show that the stress fields on the concrete between the two adjacent cracks go through a variation process from tensile stress to compressive stress with the increasing of the concrete cover thickness value. It is clear that the stress distribution and fracture spacing were related to the concrete cover thickness under the condition that the materials characteristics were certain (such as concrete and reinforcement materials).In addition, if there was a new crack produced, the location was sure in the middle of the two adjacent cracks since the maximum stress occurred in the middle of the two adjacent cracks. So, it indicates that the concrete cover thickness can influence the average fracture spacing and the crack number in the reinforced concrete prism specimen.