The invention relates to the technical field of lithium-ion batteries, in particular to a method for estimating the state of charge of a lithium-ion battery. The method includes: charging a lithium-ion battery, recording multiple groups of ampere-hour integral values, and states of charge and voltage values corresponding to the ampere-hour integral values; taking the maximum value in the multiple groups of ampere-hour integral values as the first ampere-hour integral value, the state of charge corresponding to the first ampere-hour integral value as the first state of charge, and the voltage value corresponding to the first ampere-hour integral value as the first voltage value; monitoring the lithium-ion battery in real time, recording a real-time second ampere-hour integral value and a second voltage value, obtaining a second state of charge by an ampere-hour measuring method; and if the second voltage value is consistent with the first voltage value and the second state of charge is inconsistent with the first state of charge, replacing the second state of charge with the first state of charge. The invention increases the reliable evidence for judging the online equalization of the battery pack and most importantly avoids the situation where the state of charge of the battery can be corrected only on condition that the battery pack works at the extreme state of charge, and lowers the influences of the full charge and discharge on the lifetime of the battery.