In order to study the mechanism of complex fragments production from highly excited light and medium compound nucleus induced by relatively low energy heavy ion reactions, the full statistical analysis have been performed in terms of Extended Hauser Feshbach (EHF) method. At first the charge‐ and kinetic energy‐distributions of35Cl+12Creaction at (ELab=180,200 MeV) and23Na+24Mgreaction at (ELab=89 MeV) which form the47Vcompound nucleus of almost same excitation energy are extensively investigated as a prototype of the light mass system. The variations in observed cross section from fragment to fragment are understood by the variations of binding energy of the lighter fragments of binary decay from the compound nucleus. The difference of the yield in the measured cross sections between the reactions is interpreted as the entrance channel effect that23Na+24Mgchannel has the larger critical angular momentum for fusion cross section than35Cl+12Cchannel. The measured kinetic energy distributions in the laboratory system of the complex fragments are shown to be well reproduced by the EHF‐method. Therefore the observed complex fragment production are understood as the statistical binary decay from the compound nucleus induced by heavy‐ion reaction. Next, the EHF‐method is extensively applied to the study of the complex production from the111Incompound nucleus which formed by the84Kr+27Alreaction at (ELab=890 MeV). Because the complex fragments (fissioning fragments) in the first step decay from this compound nucleus have large spins and highly excitation energies, the complex fragments decay sequentially by emitting the light particles. It is shown that the effect of multi‐step cascade decay of fissioning fragments is very important for reproducing the general trend of the observed quantities such as the observed isotope‐mass distributions.