Tensile-strained Ge quantum dot (QD) is proposed as a new route for the realization of direct bandgap conversion in Ge. Ge QDs were successfully grown on InP substrate by molecular beam epitaxy. The strain field in the QDs were analyzed by high resolution transmission electron microscopy and simulated by finite element method based on the measured geometries. The strain field in the QDs is found non-uniform and the shear component plays a significant role on the energy band structure leading to larger required hydrostatic strain than that in the Ge thin films under biaxial strain to become a direct bandgap.