Aiming at the problem that the current SOH estimation method requires a large sample size and is not suitable for tracking the results of the whole life cycle，this paper proposed a lithium battery health state estimation method based on Interacting Multiple Model（IMM） and Unscented Particle Filter（UPF） algorithm. Through the establishment of IMM model based on polynomial model，double exponential model and integrated model and the use of UPF filter to solve the problem of particle dilution in resampling process，the SOH of lithium battery was predicted according to the results of filter，and the accurate estimation of SOH in the whole life cycle of lithium battery was realized. In this paper，the selection basis and modeling method of IMM were discussed，the detailed SOH estimation algorithm was given，and the different models were compared by simulation and experiment. The simulation and experiment results show that the standard deviation of probability density function of the proposed IMM-UPF based SOH estimation result of lithium battery is only 19，which achieves high estimation accuracy.