Fast and accurate diffraction simulation for extreme-ultraviolet lithography mask with complex patterns is achieved via combination of the expanded absorber model and optimized multilayer film model. The modified thin-mask absorber model is expanded to enable simulation of absorber shifting. Equivalent-layer model and single-surface approximation model are adapted for defective and defect-free multilayer film simulation respectively. For incident angle larger than 10°, the simulation accuracy of the defective multilayer film is improved when the ideal reflection of single surface is modified with the equivalent-layer model. Simulation speed is enhanced by concurrent computing tensor product and vectorization concurrency. For defect-free mask with different simulation parameters, the modified method achieves better simulation accuracy and speed (critical dimension errors within 0.4 nm compared with the rigorous method) than the domain decomposition method. For defective mask, the critical dimension change versus absorber shifting is accurately simulated by the modified method, and the simulation errors are within 0.6 nm (compared with rigorous method) for a mask of 240 nm pitch while the modified method is 150 times faster than the rigorous method.