The differences in the structure and properties of the materials Al - 1 wt.% CNF, depending on the method of compaction, had been discussed. Carbon nanofibers allow to increase matrix strength by 30%, which corresponds to the values of cold pressing composites strength. It was shown that the results are well described by the Hall – Petch in the case of carbide phase absence. This suggests emptive effect of grain size on the materials hardness. Carbide formation at the interface takes place at 980oС, simultaneously with the destruction of the carbon fibers. In that case, hardening occurs due to new Al4C3 phase formation.