In order to reduce counting error and implement high-accuracy measurement of multi-channel asyn- chronous impulse signals with different frequencies,a cascade-connection adaptive notch filter (CANF) for real- time phase estimation is proposed.In CANF,firstly,an ANF designed by Liu (LANF) with an adaptive factor of 0 is set in the front of ANF,and the output of LANF is used as the input of an ANF designed by Mojiri (MANF). Secondly,the estimated frequency of MANF is used to adjust the frequency of LANF in real time.Then,CANF is applied to a multi-station flowmeter calibration equipment and is used to calculate the real-time phase of two chan- nels of asynchronous impulse signal.Finally,simulation and practical application of CANF are carried out,with the corresponding counting errors being less than ± 0. 047 and ± 0. 045,respectively，which means that the counting error compensation via real-time phase calculation effectively improves the counting accuracy of asyn- chronous pulses and the practicability of multi-channel parallel calibration.