Abstract: This paper makes a composite analysis upon the surrounding fields of twelve mid-tropospheric cyclogeneses. Two of them whose positions are near the average position are selected to show their vorticity and heat budgets. The resultes show that the large-scale vorticity tendency is the prerequisite of the mid-tropospheric cyclogeneses, and the contribution of the divergent term is especially notable. The geostrophic parameter (f) in lower latitudes is less than that in middle latitudes. The contribution of the divergent term, to a great entent, is dependent upon the magnitude of relative vorticity(ζ). In the middle and lower troposphere, the divergent term is the greatest, and the mid-tropospheric cyclone first grows there too. When the mid-tropospheric cyclone grows, the slope of the vorticity tube is large. As cumulus convection transports the positive vorticity from lower levels to higher levels, which makes the vorticity tube to be vertical, the mid-tropospheric cyclone is made to develop. The calculated vorticity transportation of small-scale coincides closely with the rainfall amount. The latent heat released from cumulus convection may heat the mid-tropospheric atmosphere directly, but the rise of the temperature in the upper-tropospheric atmosphere is due to the compensated dynamic descent.