Pre-sowing seed treatment in a magnetic field has advantages over other electrotechnical methods. Installations used for magnetic processing of seeds, characterized by high productivity, are safe for maintenance personnel and the environment. However, the lack of explanation of the effect of the magnetic field on the processes occurring in the seed, does not allow to establish all the effective factors in the magnetic processing of seeds and determine their optimal values. Currently, the general disadvantage of existing methods of electromagnetic stimulation is the lack of an instrumental definition of the dose of treatment. Its optimum value is determined by yield, which depends to a large extent on agro-climatic factors, soil fertility, applied cultivation technology, etc. Therefore, in order to determine the most effective modes of magnetic processing of seeds, it is necessary to develop a method for indicating its effect. The purpose of the study is to determine the influence of the magnetic field on the change in the biopotential of legume seeds. Seeds of plants undergo a variety of chemical and biochemical reactions, which are predominantly oxidative-reducing. Experimental investigations of the influence of the magnetic field on the biopotential of the seeds were carried out with seeds of peas of the Adagumsky variety and beans of the Gribovsky variety. Seeds were transported on a conveyor through a magnetic field created by four pairs of permanent magnets from the NdFeB intermetallic composite, mounted in parallel above and below the conveyor belt with variable polarity. Magnetic induction was controlled by changing the distance between the magnets and measured by a tetrameter 43205/1. The speed of the seed movement through the magnetic field is regulated by changing the speed of the conveyor belts by changing the speed of the drive asynchronous motor by means of a frequency converter. Seed treated in a magnetic field was sprouted and the values of ORP of germs were measured. The research was carried out using the experiment planning method. For this purpose, an orthogonal central compositional plan [8] was used. For the values of the upper, lower and main levels were taken for magnetic induction, respectively, 0, 0.065 and 0.13 T, for the speed of the seeds - 0,4, 0,6 and 0,8 m / s, in response - the biopotential of peas and beans. When changing the magnetic induction from 0 to 0.065 T, the biopotential increases, and with its subsequent growth begins to decrease. With magnetic induction, which exceeded 0.13 T, the biopotential of beans pea practically did not change, but exceeded its value for seeds not rooted in a magnetic field. The biopotential of the seed at pre-planting in a magnetic field is also influenced by its velocity, but in the range of 0.4-0.8 m / s it is a less significant factor than magnetic induction. The greatest values of the biopotential of leguminous seed seeds are obtained at a speed of 0.4 m / s. The studies of the change in the energy of germination and similarity of peas and beans seeds at pre-planting in a magnetic field showed that these values were the most significant for magnetic induction of 0.065 T and seed rate of 0.4 m / s. Therefore, by changing the biopotential of the seed can be determined the effectiveness of pre-sowing processing in a magnetic event. Keywords: magnetic field, peas, beans, biopotential, pre-sowing treatment of seeds, magnetic induction, seed velocity