The invention belongs to the technical field of lithium ion batteries, and specifically discloses a lithium ion battery health state on-line diagnosis method. The method includes the steps of 1, performing total-interval direct current internal resistance testing on battery samples, and calculating to obtain direct current internal resistance of the batteries at different SOC points; 2, determining a stable SOC interval of battery direct current internal resistance; 3, in a cycle use process of the batteries, performing one-time pulse charging/discharging on the batteries, and recording battery voltage change in a current abrupt change process; 4, according to the data recorded in Step 3, using the formula R=[delta]U/[delta]I to calculate internal resistance of the batteries at different time; 5, according to internal resistance values of different batteries at different time, calculating and analyzing battery polarization internal resistance change; 6, performing differentiation on internal resistance and capacity relative to the number of times of cycles to obtain a change rate distribution diagram of internal resistance and capacity; and 7, comprehensively judging the health states of the batteries, and finally adopting two pieces of data of polarization internal resistance and the internal resistance change rate to perform double judgment on the health states of the batteries.