Abstract: Ultrafast imaging system based on optical time-division multiplexing is proposed. A femtosecond fiber laser with center wavelength 1557 nm and pulse width about 90 fs, is used in the line-scan imaging system at 38.88 MHz for observing the USAF-1951 standard resolution test target. Based on the serial time-encoded amplified microscopy (STEAM) technology with the optical time-division multiplexing to achieve high resolution of ultrafast imaging, the imaging system has two times the sampling rate and the pixel number of the image is doubled. The result of the experiment demonstrates that the imaging system has achieved 20 GHz sampling rate by employing a 10 GHz of digital sampling device and doubling the sampling points comparing with the conventional ultrafast imaging system. The problem of low pixel number is addressed and image quality is enhanced effectively.