We numerically present a method to generate a high-energy square pulse in dual-amplifier figure-eight microstructured optical fiber laser (DAF8MOFL) using a genetic algorithm (GA). We explore a large region of the parameter space to find adequate parameters that promote the generation of high-performance square pulse. We demonstrate that, by utilizing the GA-based optimization technique, the parameters of the DAF8MOFL can be conveniently optimized to achieve targeted output pulse shape according to real-parameter constraints. We show that by adequately adjusting the cavity parameters, high-energy pulse with a square profile and picosecond pulse width can be obtained without the pulse breaking.