Based on the property that laser generates interference fringes on optical wedge,a device is designed to determine the wavelength of the incident laser.When laser is shining optical wedge vertically,a linear CCD is used to induce the interference fringes and output electric signal,then the signal is filtered,amplified and transformed into digital signal,which is a discrete periodic sequence with finite length.The laser wavelength can be calculated through determination of fringe gas by FFT,and three kinds of laser having wavelength of 532 nm,632.8 nm,980 nm are used for test.The test results indicate that the device has satisfactory property and perfect precision under low background.In addition,the signal wave and the experimental results can be observed intuitively on the front panel of the virtual instrument,and this device is practicable to a certain extent.