At large forward bias voltage,the accurate electrical properties of s emiconductor GaN- based blue light-emitting diode (LED) with multiple-quantum well (MQW) struct ure prepared by metal organic chemical vapor deposition (MOCVD) were measured by si ngle capacitance-voltage (C-V) method and single curre nt-v oltage (I-V) method,as well as our self-built method,respectively.After comparing the experimental results,we find that a single C-V or I-V method cannot be co nsidered as an accurate characterization method,because they can only reflect the apparent characteristics rather than the junction parameters of LEDs.However, both the apparent capacitance C_p measured by C-V method and the junction capacitance C measured by our self-bu ilt method display obvious negative value at large for ward bias and low frequency,which is in conflict with the well known Shockley′s p-n junction the ory and model which only include increasing diffusion capacitance and certainly no negative ca pacitance. Furthermore,the ideal factors of LEDs obtained from both our method and I-V method far exceed the traditional theoretical values.Finally,the accurate expressions of junction capacitance and junction conductance on voltage and frequency are obtained.These results will pr ovide an experimental basis for the study of semiconductor diode junction theory.