Due to the short history of seismic instruments record，it is difficult to know well the law of seismic activity in a short time and within a scope of small-scale，and it's thus very important to study on the historical earthquakes. The uncertainty of the seismic parameters of the historical MS≥6.5 earthquakes would have direct significant impact on some important issues such as seismicity and seismic safety evaluation. Based on the intensity distribution characteristics of MS≥6.5 earthquakes，this paper proposed an elliptical intensity distribution model based on intensity data points and fault rupture lengths. Then，we set the oval mathematical equation and the model together to establish a strong seismic parameters estimation method. Afterward we used the Monte Carlo method to analyze quantitatively the uncertainty of the resulting parameters. The results show that the accuracy of calculated magnitude using this method is within 1 and the accuracy of calculated epicenter is of Class 2. Finally，we estimated parameters of 5 historical strong earthquakes in North China. We used the mathematical model to analyze intensity data points directly in order to estimate seismic parameters of historical strong earthquake，reduced the subjective uncertainty and improved the scientific. Since the information of MS≥8.0 earthquakes is insufficient，this method is only applicable to MS6.5 to MS8.0 historical earthquakes.