Anovelhighprecision time interval measurement method is proposed in this paper. The short pulse is utilized to representthe event to trigger a specially designed highspeed ring oscillator circuit. In this way,the clock signal is generated, which issynchronized with the event.It is subsequently adoptedas the sampling clock of ADC to sample thesinusoidal reference signal. Accordingly, the time interval between the two events is mapped to the initial phase difference between the two points on the sinusoidal reference signal. The allphase fast Fourier transform (apFFT) algorithm is performed on a finite number of samples to accurately determine the initial phase difference.Then,the accurate time interval between the two events is achieved. The proposed method reduces the difficulty of engineering implementation and increases the reliability and practicability of the measurement. In the case of a sinusoidal reference signal with 10 MHz frequency, a 12bit ADC with 133 MHz sampling frequency, and apFFT with operation point number N=4 096, the singleshot time interval measurement precision of 28 ps rms and time resolution of about 1 ps can be realized. The error distribution is close to normal distribution. Experimental results are in agreement with the error budget of the theoretical analysis.