According to the outcrops,cores,slices,paleomagnetism,imaging logging and the experiment of the rock mechanical properties,the characteristics and periods of the tectonic fractures of Triassic sandstone reservoirs in the north of Dongpu sag are analyzed. It is concluded that there were NNE,NE and EW high angle tectonic fractures developed,the fracture were mostly parallel to or plumb to the main fault,the tendency was NW and SE. There were mainly developed fracture in Ermaying Formation,and rarely developed fracture in Heshanggou and Liujiagou Formation. Three periods of fracture developed. These fractures were NW extension,NNW and NWW shear crack in the Early Yanshanian,NE tension in the Late Yanshanian,NNE and NE tension,NNE shear,EW extension in the Himalayan. The analysis of the ancient-present tectonic stress field and the anisotropy of mechanical properties of rock shows that the direction of maximum principal stress of the recent tectonic stress filed and the anisotropy of rock mechanics property influenced the NW fracture of the Early Yanshanian. There were two stages fracture which were NE tension in the Late Yanshanian,NNE and NE tension,NNE shear,EW extension in the Himalayan. The results illustrate the triassic sandstone reservoir fracture characteristics and the development law.