As the largest component of Earth's time‐variable gravity field, C20 is crucial for understanding regional mass variability and climate changes. However, the C20 estimated by Gravity Recovery and Climate Experiment Follow‐On (GRACE‐FO) is currently unreliable and has been replaced by values derived from the satellite laser ranging (SLR) to ensure the proper scientific application of GRACE‐FO data products. Yet, exploring the reasons for the bias in the C20 estimates has been of great interest, as there is always a concern about the inconsistency between the SLR and GRACE solutions. This study investigates the impact of accelerometer (ACC) data processing methods on the accuracy of C20 estimation by examining the anomalous response characteristics of the GRACE‐FO ACC to the thruster. Firstly, using the statistical analysis method, we identify a correlation between the anomalous response caused by the Roll thrusters and the ACC range mode. From this basis, we make a conjecture about the mechanism of anomalous response generation, and a new thruster firing physical model based on statistical results is proposed to replace the anomalous response and optimize the current ACC data processing flow. From the results of the gravity field recovery, the corrected ACC data improve the accuracy of the estimation of C20. After multiple months of estimation, the estimate RMSD C20 between the new ACC product and the TN‐14 solutions was 1.16×10 ^-10, better than the precision of the estimate of the reference solutions. Finally, we discuss the correlation between this ACC processing method and the accuracy of C20 estimation.