A serial line scan microscopic imaging system with 1 GHz scan rate is proposed and demonstrated. This method is based on optical time-stretch in dispersive fiber to realize superfast scan imaging. Furthermore, a wavelength division technique is utilized to overcome the trade-off between high frame rate and spatial resolution caused by dispersion-induced pulse overlap. Every single frame is carved into two channels by optical filters and is detected in different wavelength bands separately. Then, both channels are combined to reconstruct the whole frame. By this method, an imaging system with spatial resolution of 28 μm at line scan rate of 1 GHz with chromatic dispersion of 1377 ps∕nm is realized. It has the potential to capture fast, nonrepetitive transient phenomena with a timescale of less than one nanosecond.