The response potential of ion selective electrode（ISE） based on metal molybdenum is easily affected by the pH value of the measured solution in the process of detecting phosphate ion(HPO

4

2-

)

which further affects the measurement performance of the molybdenum electrode.The electrochemical process of the electrode/solution interface and the influence of the pH value of the measured solution on the kinetic parameters of the electrode are studied by electrochemical impedance spectroscopy.When R（QR） or R（Q（RZ

w

）） equ

ivalent circuits are used to fit the double-layer structure of the electrode/solution interface

it can be found when the pH value of the solution being tested is 11

the charge transfer resistance R

ct

of the molybdenum electrode is the lowest

and the surface of the electrode is most reactive at this time

which is beneficial to improve the detection performance of the phosphate ion by the molybdenum electrode.The detection performance of the molybdenum electrode is evaluated by measuring a series of known concentrations of Na

2

HPO

4

solution.The experimental results show that the detection slope of the molybdenum electrode reaches-28.29 mV/（°） in the 10

-6

～10

-1

mol/L Na

2

HPO

4

standard solution with pH equal to 11

which is close to the Nernst response slope

and has a good detection performance.