One of perspective directions in plant protection is induced resistance to diseases and stresses by means of the elicitors. Biopolymer chitosan is one of the most effective elicitor, causing the local and system induced resistance. A study of biological activity of chitosan, salicylic acid (SA), chitosan+SA and the derivative of the chitin-chitosan oligomer with fragments of SA in system tomato-Meloidogyne incognita. It is shown, that addition to chitosan of salicylic acid increases its efficiency in the relation nematode. Processing of plants by, chitosan+SA in more degrees has lowered contamination of plants by nematodes, essential suppression of fertility females of nematode was marked. Showed that, N-(2-Hydroxy-3-methoxybenzyl)-N-pyridox-chitosan, which contained the pyridoxal and 2-hydroxy-3-methoxy fragments, was the most efficient, stimulating both growth and development of plants, and defense against root-knot nematode. It is obvious, that processing of plants by the investigated preparations chitosan brakes development of nematode. Comparing action of chitosan with its derivatives, it is possible to note high elicitor activity of chitosan+SA and N-(2-Hydroxy-3-methoxybenzyl)-N-pyridox-chitosan.