In a method for testing the charging and discharging reliability of a rechargeable battery, a test device measures the battery to obtain first terminal voltages and first electric currents when the battery is charged by a power supply. After the battery is discharged, the test device measures the battery to obtain second terminal voltages and second electronic currents. Based on the first terminal voltages and the first electric currents, a first lifecycle curve can be created. Based on the second terminal voltages and the second electric currents, a second lifecycle curve is created. The method compares the first lifecycle curve with a charging lifecycle curve, compares the second lifecycle curve with a discharging lifecycle curve, and generates a lifecycle estimation report of the rechargeable battery according to the comparison results.