This disclosure provides a state estimation method and a battery pack. The method includes: obtaining aging factor data, predetermined discharge data and predetermined capacity loss changing data; recording measured discharge data of a to-be-measured battery; calculating to obtain discharge voltage difference data according to the predetermined discharge data and the measured discharge data; determining a specific interval Sa according to the discharge voltage difference data, and obtaining a voltage difference statistical value ΔV2,Stats in the specific interval Sa; calculating an estimation capacity loss ΔQD of the to-be-measured battery according to the aging factor data and the voltage difference statistical value ΔV2,Stats; and determining whether the to-be-measured battery is abnormal or not according to the predetermined capacity loss changing data and the estimation capacity loss ΔQD.