The mechanism of energy conversion and radiation emission of aluminum wire array Z-pinch implosion has been studied by using a one-dimension non-equilibrium magnetohydrodynamic code. The energy transfer processes have been discused carefully, which shows that the accelerator feeds its stored energy to plasma via Poynting energy flux, and plasma kinetic energy is converted to plasma internal energy through pdV work and shock heating, thus producing radiation via several atomic processes including line radiation, recombination radiation and bremsstrahlung radiation. With the information of atomic populations, the mechanism of producing radiation has been anzlyzed. It is shown that in the implosion stage the ionization and excitation processes dominate, leading to the dominant yield of line radiation.While at stagnation most ions are in naked states, so the recombination radiation is the main radiation source. Corresponding to the two peak fractional populations of H-like and He-like ions, the line radiation also exhibits two radiation peaks at the time near peak compression. In the expansion stage, it is the radiative recombination that dominates the atomic processes, thus decreasing the share of line radiation in total radiation.