An investigation is made on the optical nonlinear characteristics of MgF_2 films containing Cu nanoparticles.When the Cu volume fraction is 0.1,at approximately ε_m + 2ε_d = 0,the film exhibits a strong thirdorderoptical nonlinear refractive coefficient of 1.0×10~(-9) cm~2/W,a nonlinear refractive index of about-4.0×10~(-7) esu,a third-order optical nonlinear response of about 6.8×10~(-8) esu,and a figure of meritof about 1.0×10~(-11).The result shows that the film may have potential applications in optoelectronictechnology. An investigation is made on the optical nonlinear characteristics of MgF_2 films containing Cu nanoparticles. When the Cu volume fraction is 0.1, at approximately ε_m + 2ε_d = 0, the film exhibits a strong third order optical nonlinearity of 1.0 × 10 -9 cm ~ 2 / W, a nonlinear refractive index of about-4.0 × 10 -7 esu, a third-order optical nonlinear response of about 6.8 × 10 -8 esu, and a figure of merit of about 1.0 × 10 ~ (-11). The result shows that the film may have potential applications in optoelectronictechnology.