A two-step time-to-digital converter (TDC) is designed based on time amplification technology, which can be applied to the field of high-precision flight measurement. This design adopts SMIC 55 nm CMOS process, uses the ring delay TDC as the coarse quantization circuit and uses the Vernier TDC as the fine quantization circuit. The accuracy of the Vernier TDC is limited by the mismatch of delay cells, which makes it difficult to break through the higher accuracy requirements in the design. The time amplifier amplifies the time margin generated by the coarse quantization and continues with the second fine quantization, which reduces the design difficulty of the fine quantization circuit. Aiming at the disadvantages of the limited input range of traditional time amplifiers and insufficient amplification accuracy, a new time amplifier structure is proposed, which has the ability to accurately amplify a wide range of input time intervals. The simulation results show that the achievable resolution of the TDC using this kind of time amplifier is 3. 7 ps, the measurement range is 80 ns, the differential nonlinearity (DNL) is 0. 73 LSB, and the integral nonlinearity (INL) is 0. 95 LSB. This design can better balance the resolution and measurement range of TDC under high linearity.