The work aims to investigate the way of controlling melt volume in nanosecond laser processing by regulating the laser pulse energy. The variation of melt volume with pulse energy was reflected through the variation of the relative height of the microstructure crater in nanosecond laser processing experiment with the pulse energy. In MATLAB environment, the finite element method based on the double temperature model simulation was used to study the effect of pulse energy on the melt volume when the nanosecond laser pulse was applied on the surface of aluminum alloy material. At low energy density, the relative height of the crater below 10% could be achieved, which was much lower than the relative height of the crater of ~100% under high energy density recorded in the literature. At low energy density, with the increase of laser pulse energy, the simulation results and experimental results showed that the melt volume decreased slightly with the increase of energy density, which was contrary to the model in the literature. In the wider energy range, the melt volume produced by nanosecond laser processing conforms to the model proposed by C K?rner et al, which shows that the melt volume in nanosecond laser processing can be controlled effectively by controlling the laser energy density. However, the abnormal variation of melt volume with energy density at lower energy density means that there are other factors that accompany this energy density to affect melt volume together, and this effect has yet to be further studied.