The invention discloses a method and system for estimating remaining available capacity of a lithium ion power battery pack. The method comprises the following steps: recording the current value in the charging process and the time used by charging, and calculating the total available capacity of the lithium ion battery at the starting time of discharging, thereby obtaining the total available capacity A of the lithium ion battery; recording the open-circuit voltage and the voltage drop delta V in the discharging process, selecting the curvilinear function used by calculating the remaining available capacity percentage through the voltage drop delta V, and obtaining the remaining available capacity percentage a of the lithium ion battery; obtaining the service efficiency of the remaining available capacity SOC of the battery at the current temperature by utilizing the relation between temperature and remaining available SOC; and adding A*a* of all the batteries to obtain the remainingavailable capacity of the lithium ion battery pack. The system for realizing the method comprises a voltage, current and temperature monitoring module for monitoring the battery pack information, themonitoring module feeds the monitored information back to the MCU, and the MCU outputs the estimated remaining available capacity of the lithium ion power battery.