A one-step wet chemical approach or seedless growth process has several advantages compared to the traditional seed-mediated growth method (SMGM), such as being simpler and not requiring a multistep growth of seeds. This study had introduced a one-step wet chemical method to synthesis gold nanoplates on a solid substrate. The synthesis was carried out by simply immersing clean ITO substrate into a solution, which was made from mixing of gold chloride (precursor), cetyltrimethylammonium bromide or CTAB (stabilizing agent), and poly-l-lysine or PLL (reducing agent). Consequently, the size of the nanoplates in the range of (0.40 - 0.89) μm and a surface density within the range (21.89-57.19) % can be easily controlled by changing the concentration of PLL from 0.050 to 0.100 w/v % in H2O. At low PLL concentrations, the reduction of the gold precursor by PLL is limited, leading to the formation of gold nanoplates with a smaller size and surface density. The study on the sample by using energy-dispersive x-ray spectroscopy (EDS) confirmed that gold peaks occurred. The optical properties of the samples were examined by a UV-vis Spectrophotometer and showed that there was no strong surface plasmon resonance band observed at UV-vis and infrared regions, which agreed to micron-sized gold nanoplates. •Gold nanoplates synthesized on the substrate using a simple one-step wet chemical synthesis approach with poly-l-lysine (PLL) as a reducing agent and CTAB as a stabilizing agent.•The nanoplate's size and surface density was strongly dependent on the concentration of PLL.•Gold nanoplates synthesized using PLL with a concentration 0.050% showed perfect triangular shape, less by-products and more homogenous in size.