The invention relates to a method for detecting the pressure of the bottom surface of a granary and a pressure sensor adopted by the method. The pressure sensor which is used for detecting the pressure of the bottom surface of the granary comprises a casing and a sensitive diaphragm, wherein an elastic cushion is arranged on the sensitive diaphragm. The method for detecting the pressure of the bottom surface of the granary adopting the pressure sensor comprises the following steps: calibrating the pressure sensor, obtaining a relational model of an output value of the sensor and the pressure and a calibration coefficient, and using the pressure sensor to detect the pressure of the bottom surface of the granary. According to contact characteristics between the sensitive surface of the pressure sensor and the bottom surface of a grain pile and an influence rule of a contacting state on the output value of the pressure sensor, the method in which the elastic cushion is additionally arranged between the sensitive surface of the pressure sensor and the bottom surface of the grain pile to improve the pressure detection accuracy of the bottom surface of the granary is provided by the invention, and the method has the characteristics of being convenient for use and maintenance, convenient for calibrating of the sensor and the like.