Abstract: Although much attention has been paid to the calculation of stress intensity factors (SIFs) on pipe cracks, the SIFs of surface cracks in thin oil and gas pipes have not been published. Three-dimensional finite element analysis has been conducted to calculate the SIF for longitudinal and circumference surface cracks in thin pipes (internal radius wall thickness >30), and the approximate calculation equations have been obtained. The results can be used for the integrity assessments of oil and gas pipes.