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We propose a square optical lattice in which some of neighbor hoppings have a Peierls phase.The Peierls phase makes the lattice have a special band structure and induces the existence of Dirac points in the Brillouin zone,which means that topological semimetals exist in the system.The Dirac points move with the change of the Peierls phase and the Dirac cones are anisotropic for some vales of the Peierls phase.The lattice has a novel hidden symmetry,which is a composite antiunitary symmetry composed of a translation operation,a sublattice exchange,a complex conjugation,and a local U(1)gauge transformation.We prove that the Dirac points are protected by the hidden symmetry and perfectly explain the moving of Dirac points with the change of the Peierls phase based on the hidden symmetry protection.