A method for measuring a temperature rise induced by bias current/bias voltage in a magnetic tunnel junction includes: (a) applying an external time-changing magnetic field to the magnetic tunnel junction; (b) measuring different first outer pin flip field values under different temperature values; (c) correlating the temperature values with the outer pin flip field values; (d) measuring different second outer pin flip field values under different bias current/bias voltage values; (e) correlating the different bias current/bias voltage-values with the measured different second outer pin flip field values; and (f) correlating temperature values and bias current/bias voltage values according to the results produced by (c) and (e). The method can determine what kind of TMR reader design provides more stable and reliable reading performance, especially under higher operational temperatures.