The stress intensity factors (SIFs) of biomaterial interface crack were analyzed using the Composite Grid Method (CGM). Two different scale grids were adopted: a coarse mesh for the whole area without considering interface crack and a fine mesh for the local singular area considering the impact of interface crack. It solved the global coarse mesh problem and the local fine mesh problem iteratively and obtained the final results. The calculation was carried out by CGM but without the demand of dense mesh near the crack tip and special crack tip elements compared with other methods. The numerical extrapolation method of determining the SIFs to avoid the oscillation singularity of asymptotic fields of elastic interface crack. Reasonable agreement was achieved and efficiency of CGM for such kind of problem was displayed.