AuNP decorated GO nanocomposites (GO-Ph-AuNP) via aryldiazonium salt chemistry have been successfully prepared, which can be used as the immobilization matrix for loading glucose oxidase (GOx) towards a sensitive glucose sensor. The fabricated nanocomposite was characterized by field emission scanning electron microscopy, UV-Vis and electrochemistry. The direct electrochemistry of GOx was successfully realized on GO-Ph-AuNP modified GC electrodes with a heterogeneous electron transfer rate constant of 8.3 s-1, revealing fast direct electron transfer of GOx. The GOx immobilized on GO-Ph-AuNP nanocomposite modified electrode retained good electrocatalytic activity toward glucose over a linear concentration range from 0.3 to 20 mM with the sensitivity of 42 μA mM-1 cm-2 and enzyme turnover rate of 112 s-1. In addition, the fabricated biosensor was capable of monitoring glucose consumption by live cells.