A general coupled-wave model is presented for square-lattice photonic crystal (PC) lasers with transverse-electric polarization. This model presents a realistic treatment of the full three-dimensional structure of typical laser devices by incorporating the surface emission and high-order coupling effects. Numerical examples based on our model are presented for various PC structures with different air-hole shapes. The accuracy of the results is verified using three-dimensional finite-difference time-domain simulations. Using this model, we demonstrate that the PC lattice with asymmetric air holes can give rise to a high-output power, efficient device.