The invention relates mainly to a method for controlling the motion of a yarn stopper magnet in a measuring feeder for textile machines, preferably for weaving machines of air-or waterjet-type. The stopper magnet has a soft-iron armature connected to a yarn stopper element, which armature co-acts with at least one electromagnetic coil in order to achieve the desired motion of the stopper magnet. During an initial part of the time for the motion, according to the invention, said electromagnetic coil/-coils is/are supplied with a control voltage with an amplitude considerably exceeding the average level of the control voltage during the remaining part of the motion, in order to achieve an optimally fast motion with low input energy amount and thereby a low heat development, as well as low kinetic energy (speed) of the stopper element at the end of its motion.