Abstract: In order to generate 2μm laser,a novel method was presented with kalium titanyl arsenate(KTA) as a nonlinear crystal in optical parametric oscillators.It was proved feasible by comparing the nonlinear parameters between KTA and KTP crystal.The graph of the relationship between the wavelength and the tunable-angle was drawn based on Sellmeier equation and refractive index ellipsoid of KTA.After compareson it was found that the crystal has better nonlinear characteristic at cut angles of φ=0°,θ=48.37°.Then the walk-off angle,acceptance angle and bandwidth were calculated.The basic problems on the design of KTA-OPO were solved and the study foundation was built up for the future experiments.