The invention relates to a method of manufacturing a composite turbomachine blade, the method comprising the following steps: a) making a preform by three-dimensionally weaving yarns including tracer yarns disposed at least at the surface of the preform; b) cutting out said preform so as to leave intact a series of tracer yarns situated along a reference face of the preform; c) pre-deforming said cut-out preform; d) compacting and stiffening said pre-deformed preform; e) providing an injection mold in which said stiffened preform is placed; f) heating said injection mold; g) injecting a binder into said injection mold, the binder comprising a thermosettable resin; and h) extracting from the mold a composite molded part presenting substantially the shape and the dimensions of said blade. The invention is applicable to a making fan blade.