The catalysis mechanism of PbNTO salt (PNTO) in GAP propellant combustion was investigated by means of modern diagnostics.It is found the catalysis mechanism of PNTO is quite different from that of the common Pb salt.PNTO is the burning centre,the combustion of the propellant is speeded up at the site where PNTO is situated.At the presence of PNTO as a single catalyst,the combustion rate pressure exponent of RDX/GAP/NG propellant decreases to the level of about 0.5.