Abstract: By analyzing two kinds of meso-scale low vortices with heavy rainfall, the comparison study of their physical structure, energy variation and conversions has been made. It indicates that for the landing tropical cyclone, the temperature-pressure field is more symmetric with very strong upward motion in its middle. Therefore, its vorticity, correspondingly .the rotational winds kinetic energy K_φ is larger than the one of the baroclinic vortices. However, the latter one occurring on a shear line has a typical structure with strong convergence in lower levels overlapping a divergence centre in the higher levels. The temperature gradient near the vortex centre is rather clear. It is notable that the divergence winds kinetic energy K_x related to the divergent field for the former one is much larger than the one in tropical cyclone during their development period, though the meso-scale low on the shear line seems very weak appearing at the isobar maps. A large amount of potential energy P transfers to K_x and becomes the major energy source during the strengthening period of the tropical cyclone. For the mesoscale low on the shear line, the energy conversion from K_x to K_φ is very strong through the whole period. It is verified further from this study that the energy conversion from K_xto K_φ is an important step for the development of meso-scale low vortex either for the tropical or the baroclinic one. This kind of conversion will be more active when the potential energy P is released in a large amount.