The modified plane-wave expansion method for calculating quickly the band structure is used to study the band structure in two rectangle lattice 2D photonic crystals. The large absolute band gaps are found at high frequency field, and parameters is op timized. When the unit cell is like the Chinese word“工”, an absolute band gap Δω =0. 1393ωe (whereωe = 2πc / a, a is the lattice constant , c is light speed) is found at a high frequency field, which mid - frequencyωmid = 1. 7368ωe ,Δω/ωmid = 8.02%. When the unit cell is like the Chinese word“王”, a larger ab=solute band gapΔω = 0. 1544ωe is also found at a high frequency field, which mid-frequencyωmid = 1. 5854ωe ,Δω/ωmid = 9. 74%.