In a digital particle image velocimetry(DPIV) system,the superior limit of measurable velocimetry depends on the time interval between two particle images.To measure a high velocity,the time interval should be as sort as possible.Frame straddling technology,which highly depends on professional high speed camera,is widely used in DPIV system to reduce the time interval between two particle images.But,by using frame stradding,the time interval must be larger than frame pitch.We describe in this paper a new method,which based on multi-wavelength pulse laser beam illumination and multispectral imaging,to reduce the time interval instead of frame straddling.Using this method,the time interval between different particle images just depends on the pulse interval time of different wavelengths,and it is independent of the frame rate of the camera.A double-wavelength DPIV system is built,and the time interval between two particle images can be reduced to 50 nanoseconds.