The invention discloses a double-
constant current source structure-based high-resolution fast time interval measurement circuit. Based on a time-to-amplitude converter, a double-
constant current source structure composed of a discharging 
constant current source and a charging 
constant current source is adopted, and a charging and discharging 
capacitor is charged through the charging 
constant current source, so that the 
voltage of the charging and discharging 
capacitor can return to initial 
voltage. According to the double-
constant current source structure-based high-resolution fast time interval measurement circuit of the invention, the charging constant 
current source has two kinds of working states; and under the control of on-off control signals, the magnitude of the charging current of the charging constant 
current source can be changed, namely, the charging constant 
current source optionally generates micro current according to measuring 
process requirements in an initial preparation measuring phase, a discharging phase and an ADC sampling stage, and so as to provide stable initial 
voltage for the charging and discharging 
capacitor in the initial preparation measuring phase, and after measurement is completed, the charging constant current source optionally generates 
high current to charge the charging and discharging capacitor, so that the voltage of the charging and discharging capacitor can be restored rapidly, and therefore, time interval measurement speed can be improved. With the double-constant current 
source structure-based high-resolution fast time interval measurement circuit adopted, the time interval measurement speed can be improved greatly with measurement accuracy ensured, and therefore, random equivalent sampling waveform reconstruction efficiency can be further improved.