Abstract: The high-precision time-interval measurement technique is used to measure the velocity of light in the laboratory environment. The light velocity can be precisely calculated by measuring the propagation delay time of light in the zerodispersion single-mode fiber, whose length and refractive index are already known. By theoretical derivation, the relationship between the fiber length L, the refractive index n and the fiber delay time τ was deduced, and the light velocity can be calculated by L, n and τ. Compared with the traditional measurement methods of astronomy or the measurement methods with precise instruments, the high-precision time-interval measurement technique can improve the time resolution to 125ps. Two or three simple instruments were used only to get the accurate measurement result in the laboratory environment. The measurement result of the light velocity is 299928077m/s, and the measurement error is 30860m/s.