Purpose: The purpose of this study was to evaluate the effect of a six month web-based diabetic education on plasma glucose in people with diabetes. Method: A randomized design with control and experimental groups being assessed pre- and post-intervention was used. Seventeen patients were randomly assigned to a control group and 18 to an experimental group. Participants were requested to input the blood glucose level weekly to http://www.biodang.com by cellular phone or wire Internet for 6 months. The researcher sent optimal recommendations to each patient using the short message service (SMS) for cellular phone and wire Internet. Messages were sent weekly for 6 months. Results: Glycosylated hemoglobin ($HbA_1c$) decreased 1.5 percentage points at 3 months and 1.4 percentage points at 6 months compared with baseline in the intervention group. Patients in the intervention group had a decrease in 2 hours post meal glucose (2HPMG) of 94.3mg/dl at 3 months and 82.5mg/dl at 6 months compared with baseline. Conclusion: This web-based intervention using SMS for cellular phone improved HbAlc, and 2HPMG for six months in patients with type 2 diabetes.