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The high-energy rectangular pulse dissipative soliton (DS) is achieved in a long-cavity sigma-shaped configuration erbium-doped fiber laser.A long fiber is inserted in the linear arm of the sigma-shaped configuration to extend the resonator length twice,which effectively improves the pulse energy.The nonlinear polarization rotation technique is employed to realize the mode-locked state.Stable rectangular pulses with pulse energy of 421.22nJ are obtained at the pump power of 620 mW.To the best of our knowledge,this high pulse energy is a new record of the rectangular pulse mode-locked DS fiber lasers.