Abstract: Chalcogenide glasses were possessed of some unique advantages, such as large infrared transmission window(up to 25 m), low phonon energy(lower than 350 cm-1), large glass forming region and highly nonlinear refractive coefficient n2(about 100-1 000 times than silica). With excellent optical nonlinear,calcogenide glass photonic crystal fiber had a large number of potential applications in the infrared filed. A highly nonlinear photonic crystal fiber based on Ge20Sb15Se65 chalcogenide glass was designed. Using plane-wave method(PWM), numerical analysis of its nonlinear and dispersion characteristics with different structure parameters were carried out. By optimization structural parameters, a highly nonlinear and broadband dispersion-flattened fiber was obtained. With a 3.4 m laser pumping, signal light could be effectively amplified in 3.3-3.5 m.