Method for manufacturing a testing head of a non-destructive testing sensor based on eddy currents, this testing head comprising at least two coils (E, R +, R -; E/R +, E/R -) having transmission and/or receiving functions, comprising the following steps: - optimizing a geometric design (P i, P f) of the coils (E, R +, R -; E/R +, E/R -) of the testing head based on at least one of the following criteria: • minimizing an electromotive force E induced in at least one coil having a receiving function (R +, R -; E/R +, E/R -) when the testing head is at a predetermined nominal distance from a part to be inspected free from defects, • maximizing a variation Δe of said induced electromotive force E, this variation Δe being due to the presence of a standard defect to be detected in the part to be inspected when the testing head is at said nominal distance from the part to be inspected, - manufacturing the testing head in accordance with the geometric design (P i, P f) of the coils (E, R +, R -; E/R +, E/R -) carrying out this optimization, and - the optimization of the geometric design (P i, P f) of the coils (E, R +, R -; E/R +, E/R -) is further carried out based on at least one criterion (C2, C3) for optimizing a further variation ΔE of said induced electromotive force E, this further variation ΔE being due to a variation in distance between the testing head and the part to be inspected, characterized in that: - the optimization of the geometric design of the coils comprises optimization of geometric dimensions (P f) of each of these coils (E, R +, R -; E/R +, E/R -). - optimizing a geometric design (P i, P f) of the coils (E, R +, R -; E/R +, E/R -) of the testing head based on at least one of the following criteria: • minimizing an electromotive force E induced in at least one coil having a receiving function (R +, R -; E/R +, E/R -) when the testing head is at a predetermined nominal distance from a part to be inspected free from defects, • maximizing a variation Δe of said induced electromotive force E, this variation Δe being due to the presence of a standard defect to be detected in the part to be inspected when the testing head is at said nominal distance from the part to be inspected, • minimizing an electromotive force E induced in at least one coil having a receiving function (R +, R -; E/R +, E/R -) when the testing head is at a predetermined nominal distance from a part to be inspected free from defects, • maximizing a variation Δe of said induced electromotive force E, this variation Δe being due to the presence of a standard defect to be detected in the part to be inspected when the testing head is at said nominal distance from the part to be inspected, - manufacturing the testing head in accordance with the geometric design (P i, P f) of the coils (E, R +, R -; E/R +, E/R -) carrying out this optimization, and - the optimization of the geometric design (P i, P f) of the coils (E, R +, R -; E/R +, E/R -) is further carried out based on at least one criterion (C2, C3) for optimizing a further variation ΔE of said induced electromotive force E, this further variation ΔE being due to a variation in distance between the testing head and the part to be inspected, - the optimization of the geometric design of the coils comprises optimization of geometric dimensions (P f) of each of these coils (E, R +, R -; E/R +, E/R -).