A novel approach of asymmetrical gradient coil design for head imaging in MRI (magnetic resonance imaging) is presented in this paper. The design is based on a modified target field method in which the stream function is introduced to replace Blaines scheme for the length control. The transverse head coil calculated by this method has a high performance. The coil efficiency is 0.41 mT/m/A and the inductance is 512 μH. The coil has an inner diameter of 32 cm and a length of 45.8 cm. The size of the ROU (region of uniformity) is 20 cm along the transverse direction and 17 cm along the axial direction and it is close to one end of the coil. The ROU of the coil matches the ROI (region of interest) of human head very well. Compared with previous designs, our design has relatively high performance and the overlap between the ROU and the ROI is larger (the overlap percent is 95 % ).