Silver nanoparticles were synthesised successfully using poly(2-acrylamido-2-methylpropane sulphonic acid) (PAMPS) as a surfactant. Silver nanoparticles prepared through this approach possess high purity and narrow size distribution. The size distribution result shows that the diameters ranging from 78.82 to 105.709 nm can account for 76.41% of nanoparticles. UV–vis spectra were used to record the formation of silver nanoparticles in detail. It is found that PAMPS can play an important role in the formation and the colloidal stabilisation of silver nanoparticles because of the high affinity of sulphonic and amide with silver ions. The formation is summarised in detail. In addition, a potential application in nanocomposites of this method is explored. The Ag/polyaniline (PANI) nanocomposite prepared using this method shows higher electrical conductivity than that prepared using other methods. This method is novel, convenient, efficient and environmental-friendly, especially suiting those wastewaters treatment facilities containing silver ions. At the same time, it is also promising to prepare Ag/PANI or other metals/polymer composites via in-situ polymerisation.