The method based on saddle-shaped magnetic field waveform to calculate the position of linear motor can provide a new choice for cost-effective position calculation. It includes two parts: offline database establishment and real-time calculation. In real-time calculation, interval matching is the key. The relationship between the double-saddle magnetic field values is analyzed, and the real-time algorithm of matching and determining interpolation interval by point distance is put forward, in which the interpolation interval is determined by combining point distance and change trend of special points. In addition, the influence of data fluctuation and the total amount of database information on the calculation is also studied. Compared with the results of the samples, the calculation method using point distance has clear physical meaning, and the calculation accuracy can be regulated and optimized through adjusting the height parameters of data collection and the total amount of database data, so it has a good research value and application prospect.