A method for monitoring the operating state of a turbomachine hydro-mechanical unit of an aircraft, said hydro-mechanical unit comprising - a metering valve, comprising a movable metering part and allowing the generation of a passing flow rate, depending in particular on the position of this movable part, - a control valve configured to maintain a predetermined pressure difference (ΔP) at the terminals of the metering valve in order in particular to control the flow rate through the metering valve, - a flow rate meter able to measure the mass flow rate of fuel passing through the metering valve, wherein a monitoring module is configured for implementing the method according to the following steps: - (E20') determining a reconstructed flow rate based on the position of the movable part measured by a position sensor of said part, and on a measurement of the density of the fuel, - calculating a residue corresponding to the difference between the real flow rate measured by the flow rate meter and the reconstructed flow rate, and comparing the residue to a determined threshold value, and - determining an abnormal operating state of the hydro-mechanical unit depending on the result of the comparison, wherein the steps of determining a reconstructed flow rate and of calculating the residue are implemented for different stabilized points of the flight envelope of the aircraft, allowing obtaining a vector of residues, the vector of residues being compared to a vector of determined threshold values for the different stabilized points in order to determine the operating state of the hydro-mechanical unit, and wherein, if the residue is less than the determined threshold value, the residue is stored in a memory of the monitoring module. - a metering valve, comprising a movable metering part and allowing the generation of a passing flow rate, depending in particular on the position of this movable part, - a control valve configured to maintain a predetermined pressure difference (ΔP) at the terminals of the metering valve in order in particular to control the flow rate through the metering valve, - a flow rate meter able to measure the mass flow rate of fuel passing through the metering valve, wherein a monitoring module is configured for implementing the method according to the following steps: - (E20') determining a reconstructed flow rate based on the position of the movable part measured by a position sensor of said part, and on a measurement of the density of the fuel, - calculating a residue corresponding to the difference between the real flow rate measured by the flow rate meter and the reconstructed flow rate, and comparing the residue to a determined threshold value, and - determining an abnormal operating state of the hydro-mechanical unit depending on the result of the comparison, - (E20') determining a reconstructed flow rate based on the position of the movable part measured by a position sensor of said part, and on a measurement of the density of the fuel, - calculating a residue corresponding to the difference between the real flow rate measured by the flow rate meter and the reconstructed flow rate, and comparing the residue to a determined threshold value, and - determining an abnormal operating state of the hydro-mechanical unit depending on the result of the comparison, wherein the steps of determining a reconstructed flow rate and of calculating the residue are implemented for different stabilized points of the flight envelope of the aircraft, allowing obtaining a vector of residues, the vector of residues being compared to a vector of determined threshold values for the different stabilized points in order to determine the operating state of the hydro-mechanical unit, and wherein, if the residue is less than the determined threshold value, the residue is stored in a memory of the monitoring module.