Self-assembled monolayer（SAM）of 3-Aminopropylmethyldiethoxysilane（APMDES）absorbed on the surface of glassy carbon electrode is constructed, and the electrode is modified with -NH2 group. Then low concentration of bovine serum albumin is detected by the modified electrode，and compactness of the monolayer and the sensitivity to detecting bovine serum albumin are studied by gold-label promoted silver-staining. The result indicates that the compact monolayer can be obtained when the concentration of APMDES reaches 3-vol. % in alcohol solution, the assembling time is 4 hours and the assembling temperature is 30 ℃. Under the above conditions，the peak currents are linear to the concentration of albumin over the wide range from 0.5 to 0.05 ng/mL，and the detection limit is 0.02 ng/mL，the regress linear equation is I（μΑ）= 0.825 4+1.431 9（C（ng/mL），R=0.958，and the background current signals are less than 2.0×10-7 (A).