The aim of the submitted study is to realize carrier-free immobilization (as cross-linking enzyme aggregates) of Aspergillus niger Glucose Oxidase enzyme, to determinate the optimum immobilization conditions, and to investigate the properties of immobilized enzyme sets. Carrier-free enzyme immobilization was realised by forming cross-linked glucose oxidase enzyme aggregates (CLEA’s). Different precipitants were used in different media conditions during forming CLEA’s. The “immobilized enzyme activity” was measured by activity determination method with the use of glucose substrate. The optimum conditions which were determined in the light of the experiments for the cross-linked enzyme aggregates can be summarized as; the initial enzyme concentration, 0.05 mg/ml; the optimum temperature, 25ºC; the precipitant type, BSA; the precipitant concentration, 5 mg/ml; the concentration of glutaraldehyde, 2% (v/v). After determining the optimum conditions, glucose solutions at different concentrations (1.0-4.0 mg/dl) were prepared for investigating the performance of the glucose oxidase aggregates. The kinetic parameters were calculated by Lineweaver-Burk plots such as; K_m =0.0115 mM; V_m =1.206 mM.min^-1 for native enzyme and K_m = 0.025 mM; V_m =0.593 mM.min^-1 for cross-linking enzyme aggregates.