A positioning method of a variable rate fertilizer applicator with sensors is introduced, to replace GPS in precision agriculture. In the positioning system, the controller receives pulse signals from the sensor and calculates the working distance of the variable rate fertilizer applicator, thus the grid in which the fertilizer applicator is working is identified by the algorithm of automatic grid recognition. The accumulative error of the system from the sensor is corrected by the error revising algorithm, and the correction results were tested in field. The experiment results showed that the accumulative errors for the photoelectric encoder and the proximity transducer are 2.32 m and 2.34 m, within 250?m of working distance, respectively, i.e. the positioning errors is less than 6%. Under the above conditions, a variable rate fertilizer applicator can be applied in a larger working field if the working grid is divided longer.