Method for controlling the weft insertion system of a gripper loom wherein a carrying gripper and a drawing gripper are alternately driven, inside the shed formed between the warp threads, by a pair of toothed wheels through corresponding flexible straps bearing at one end said carrying gripper and said drawing gripper, respectively, wherein each of said straps is meshed on a respective toothed wheel by means of a series of slots longitudinally formed in the body of the strap, and said strap is kept adherent to a sector of said toothed wheel by means of guide slides, said system operation being monitored by a central control unit of the loom, said controlling method including the steps of: a.detecting the surface temperature at rest (Ti) and the surface temperature under friction (Tf) of the flexible straps during the loom operation; and b.calculating parameters which are representative of the loom operation on the basis of the surface temperature at rest (Ti), the surface temperature under friction (Tf) of the straps, the difference between said temperatures (ΔT), and their variations over time; characterized in that as a surface temperature at rest (Ti) of the straps the room temperature in the proximity of said straps is taken, said room temperature being indirectly detected as the temperature of the lubricating oil in a tank of lubricant on-board of said loom, and in that said method further comprises the steps of: c.comparing said parameters which are representative of the loom operation with respective predefined threshold values; d.separately considering exceeding of the threshold values i. by a first group of parameters, relative to the temperatures of the straps, and ii. by a second group of parameters, relative to the gradient of variation of said temperatures of the straps over time; e.sending alert messages to the operator or command messages to the central control unit of the loom which indicate the achievement of limit wear conditions of one or more of the components of the weft insertion system, when the actual values of the parameters of said first group of parameters exceed their respective threshold values, whereas the actual values of the parameters of said second group of parameters do not exceed their respective threshold values; and f.sending alert messages to the operator or command messages to the central control unit of the loom, which indicate a possible incorrect mechanical adjustment of the components of the weft insertion system, when the actual values of the parameters of said first group of parameters and of said second group of parameters both exceed their respective threshold values. a.detecting the surface temperature at rest (Ti) and the surface temperature under friction (Tf) of the flexible straps during the loom operation; and b.calculating parameters which are representative of the loom operation on the basis of the surface temperature at rest (Ti), the surface temperature under friction (Tf) of the straps, the difference between said temperatures (ΔT), and their variations over time; c.comparing said parameters which are representative of the loom operation with respective predefined threshold values; d.separately considering exceeding of the threshold values i. by a first group of parameters, relative to the temperatures of the straps, and ii. by a second group of parameters, relative to the gradient of variation of said temperatures of the straps over time; i. by a first group of parameters, relative to the temperatures of the straps, and ii. by a second group of parameters, relative to the gradient of variation of said temperatures of the straps over time; e.sending alert messages to the operator or command messages to the central control unit of the loom which indicate the achievement of limit wear conditions of one or more of the components of the weft insertion system, when the actual values of the parameters of said first group of parameters exceed their respective threshold values, whereas the actual values of the parameters of said second group of parameters do not exceed their respective threshold values; and f.sending alert messages to the operator or command messages to the central control unit of the loom, which indicate a possible incorrect mechanical adjustment of the components of the weft insertion system, when the actual values of the parameters of said first group of parameters and of said second group of parameters both exceed their respective threshold values.