The invention discloses a battery charge state estimation method and system. The estimation method comprises the following steps: S1: acquiring charge and discharge data of a to-be-tested battery andcalculating a characteristic variable of the to-be-tested battery according to the charge and discharge data; S2, inputting the characteristic variable of the to-be-tested battery into a correlation model representing a quantitative relationship between the characteristic variable and the maximum available capacity to obtain a maximum available capacity of the to-be-tested battery; and S3, acquiring a remaining capacity of the to-be-tested battery and estimating a charge state of the to-be-tested battery based on the remaining capacity and the maximum available capacity. According to the invention, on-line estimation of the current maximum available capacity of the battery is realized and then SOC calculation of the full life cycle of the battery is realized, so that a problem of increasing of an SOC estimation error with attenuation of the battery capacity is solved. Moreover, the algorithm is simple and practical and the complexity is low. The estimation method is suitable for an embedded BMS system.