The existing binary defocusing techniques have excellent performance in the measurement speed, while the measurement precision is not high. We propose a mixed binary defocusing method, which combines the respective advantage of one-dimensional modulation defocusing techniques and two-dimensional modulation defocusing techniques. The mixed binary defocusing method adopts the frequency-dependent property of these two kinds of methods to approach the sinusoidal fringe patterns. The optimized pulse width modulation technique is selected to produce high-frequency binary patterns, and the improved error diffusion dithering technique is selected to generate low-frequency patterns. Then the phase-shifting method is adopted to obtain the wrapped phase from the defocused pattern, and the absolute phase is obtained with a multiple-wavelength phase unwrapping method from these wrapped phases at different frequencies. With the standard of the root mean square error of the wrapped phase, different defocusing methods are compared in the simulation. The measurement surfaces are compared in the real object measurement. The results verify the frequency-dependent property of these two kinds of methods and the proposed method has a greater performance than any one binary defocusing technique.