The invention provides a method for preparing a graphene electrode in a high-temperature piezoelectric sensor. The method includes the following steps that a pretreated high-temperature piezoelectric crystal plate of the high-temperature piezoelectric sensor is placed into a plasma chemical vapor deposition cavity, the cavity is closed, and a vacuum pump is started; when air pressure inside the cavity is lowered to 10<-5> Torr or below, shielding gas and carbureted hydrogen gas are connected in to adjust the pressure intensity inside the cavity; and a vacuum reacting furnace is started for heating and warming, a plasma source is switched on to perform constant temperature deposition, and accordingly the graphene electrode can be obtained. According to the preparation method of the graphene electrode, the high-temperature piezoelectric crystal plate is used as a substrate, a small or large number of layers of graphene are grown on the surface of the crystal plate without metal catalysis as the electrode through the plasma enhanced chemical vapor deposition (PECVD) technique directly, adhesive force between a graphene thin film and the crystal plate is good, and electrical conductivity of the graphene thin film is excellent.