Needle bearing is one of the most important parts for gear pump and it restricts the service life of the pump. It is significant to research the mechanism of failure and optimal design for needle bearing and the service life will be increased. Aimed at problem of failure of needle bearing of external gear pump， the gear pump is used as the research object. The force of bearing was calculated by means of computational fluid dynamics (CFD) and lubrication was designed for bearing to confirm its dimension. It would be used engineering logarithmic roller crowning to overcome edge effect and to improve eccentric load effect. Based on the tested results, the service life of improved gear pump will increase 20% than before, in the 25 MPa overload test. The method to optimize the bearing will give theoretical basis to design gear pump and needle bearing, and increase its service life.