The diurnal, seasonal and solar cycle variations of ionospheric electron content (IEC) are studied. An attempt has been made to develop an empirical model for the IEC at Lunping (25 degN,121.2 degE) using harmonic analysis. The proposed model predicts the diurnal variation of the monthly mean values of IEC for any month for sun spot numbers up to 150. The amplitudes and phases of all harmonic components show seasonal and solar cycle dependences. The daily mean IEC and the amplitude of the first order harmonic depend seriously on the solar activity. A set of 81 coefficients of the zero and first four orders is determined and found to be sufficient for modelling the IEC. The agreement between observed and modelled IEC values is rather good; maximum deviation is limited to +/-15% in winter and 10% in summer and equinox. The agreement between observed and modelled IEC values is remarkably good in May and is generally better in years of moderate solar activity.