Abstract: Using the data from observation on Chinese research vessel Xiang Yang Hong No.5 and other sources during AMEX Phase Ⅱ, the kinetic energy budget and circulation background of tropical storm Irma was analyzed.Irma was formed on the ITCZ of the Southern Hemisphere. That the easterlies trade and westerlies monsoon on both sides of the ITCZ strengthened, the strong divergent flow in upper troposphere emerged, and the Richardson number (Ri) in middle and lower troposphere decreased to a minimum, contributed much to the formation of Irma. The largest contribution to increasing kinetic energy in the general flow was generation term-V·∇ø.As to the generation term, the conversion of available potential energy to kinetic energy-ωα was the largest contribution. It suggested that strong ageostrophic acceleration was existed, and the internal sources and the ensemble effect of cumulus convection played an important role in increasing kinetic energy of Irma.To the increasing of eddy kinetic energy during the period of Irma rapidly intensifying, the most important source was dissipation term and the minor source was the energy conversion from the kinetic energy of area-mean flow to eddy kinetic energy. Therefore, the eddy kinetic energy of developing tropical disturbance is extracted both from smaller and larger scale motion. On the other hand, the disturbance generates and exportes eddy kinetic energy to enviromental atmosphere acting as a generator and exporter of eddy kinetic energy.