To explore the applications of time of flying technology for short to medium distance measurement, a scheme for optical fiber refractive index and length measurement is introduced, which is based on the TDC7201 chip that apply time of flying technology principle. The measureme nt system is made up of some devices and modules, such as TDC7201, microcontrolle r, laser transmitter and laser receiver, and the fiber length measurement range is 2 cm to 100 km in theory. The experiment platform is established, and then the refractive index or length of 1 cm, 2 cm, 3 cm and 1.5m, 5.1m, 20 km, 70 km, 90 km fiber are measured. The result shows that the minimum measurement length is 1 cm, the maximum measurement length over 90 km, and the standard deviation of 5.1 m fiber length measurement is 0.9 mm.