To improve the meshing performance ol internal double helical gear with high speed，a multi-objective optimal design approach considering the influences of deformation of elastic shaft is proposed. The load distribution on tooth contact line and tooth deformation in a meshing period are got by the tooth contact analysis and loaded tooth contact analysis. The local friction coefficients of discrete points on tooth contact line are determined by the regression equation which is based on the mixed elastohydrodynamic lubrication model，and then the Blok’s basic equation is used to get the surface flash temperature with high speed. After that，applying the genetic optimization algorithm，the tooth modification values are determined to optimize the amplitude of loaded transmission error，flash temperature and load distribution. The calculation is illustrated by a numerical instance. The results show that with and without misalignment error， after the tooth modification， both ALTEs decline significantly， and the surface flash temperature obviously decreases at the coming into and out of contact zones. Meanwhile，the edge contact is avoided，and both the load distributions are improved. The calculation results of the proposed optimization design method are reliable，and the method presented is an effective means for tooth dressing of high speed gear drives.