The formation of the professional of Education in other sceneries and contexts has been one of the variants assumed by our educational model in its improvement. The wholesome character of its formation considers, in its large extend, its holistic and continued formation as a consequence of the solution to professional problems. One of these demands is considered to be the conceptual formation of the pre-professionals who study to be High School professors, as the educational level in which the experience we refer to has been developed. Such pretensions will be put into practice at the time of elaborating the concept of magnitude, as a systematizing concept of the mathematical knowledge from a didactic vision, to be considered in the formation of the professional of Education in the field of Exact Sciences.