A new method to measure time-of-flight in pulse laser ranging is proposed. Considering time-of-flight errors of the conventional method are caused by counting during the first and last cycles. The n clock-pulses with the same frequency and uniform distribution phases are generated by the PLL unit in ses during the period respectively in the an FPGA chip, in which n counters, count the pulsame chip. The average of n is the final result. It is just like that a cycle T is divided into N parts,and each one works as a pulse,whose cycle is T/N. Therefore the measurement precision is improved as much as n times without increases of time consumption and dead time.