A method for measuring the surface level of liquid metal and the surface level of slag in the crucible of a metallurgical shaft furnace having an external wall provided with a shielding made of steel, as well as a tap hole, the shielding of the external wall surrounding a refractory thickness in contact with the liquid metal, the shielding being provided on its external surface with a plurality of strain gauge sensors and with one or more thermal sensors, said sensors (6,7) being mounted so as to be aligned in a vertical plane, on either sides of the tap hole and such that the two types of sensors are alternated in this vertical plane, said method comprising the following steps of: - measuring the following variables at a number of points of the external wall of the crucible: - the circumferential strain of said external wall by means of the strain gauge sensors attached onto said shielding; - the temperature of said external wall by means of thermal sensors attached onto said shielding; - optionally measuring the circular pressure or static pressure of the hot blast in the furnace; - introducing said variables measured at a number of points of the external wall of the crucible in the general equation governing the continuous circumferential strain the solution of which is analytical, and which contains two unknown values, the level of liquid metal and the overall level of liquid metal-slag, taking into consideration the following established parameters: the geometry of the shaft furnace, the parameters representative of the nature of the constituent materials of the shaft furnace, the thickness of the external wall of the shaft furnace at each point of measurement, the density of the liquid metal and of the slag; and - solving said equation and obtaining the surface level of liquid metal and the surface level of slag in the crucible. - measuring the following variables at a number of points of the external wall of the crucible: - the circumferential strain of said external wall by means of the strain gauge sensors attached onto said shielding; - the temperature of said external wall by means of thermal sensors attached onto said shielding; - the circumferential strain of said external wall by means of the strain gauge sensors attached onto said shielding; - the temperature of said external wall by means of thermal sensors attached onto said shielding; - optionally measuring the circular pressure or static pressure of the hot blast in the furnace; - introducing said variables measured at a number of points of the external wall of the crucible in the general equation governing the continuous circumferential strain the solution of which is analytical, and which contains two unknown values, the level of liquid metal and the overall level of liquid metal-slag, taking into consideration the following established parameters: the geometry of the shaft furnace, the parameters representative of the nature of the constituent materials of the shaft furnace, the thickness of the external wall of the shaft furnace at each point of measurement, the density of the liquid metal and of the slag; and - solving said equation and obtaining the surface level of liquid metal and the surface level of slag in the crucible.