Ionosphere is the region in the upper atmosphere where there are sufficient amount of electrons and ions to influence the propagation of radio wave. For radio wave propagation studies and application, a standard model (model based on data) such as IONEX map model was developed to study the ionospheric parameter i.e. the Total Electron Content. This parameter is used to quantify the level of ionization in the ionosphere. The performance of IONEX map model over Ilorin with station coordinate 4.67degreeE longitude and 8.48degreeN latitude has been studied using 366 days in the year 2012 TEC data and the result is compared with the monthly average of the observed value for each month in year 2012. It was observed that the performance of IONEX map model is better within the period of January to May whereas there were large overestimation in TEC values in the month of June to December.