A simple and green chemical reduction method to the synthesis of chitosan capped cupric oxide (CuO)NPs using different reducing agents, i.e. glucose, ascorbic acid, urea, thiourea in aqueous solution under ambient condition in the presence of chitosan as capping agent and we got different morphologies for CuO NPs like, nanocubic and nanoflake-like structures. A typical procedure simply involved the thermal oxidation of these substrates in air and within the temperature range from 60 to 70 °C. The advantages of this synthetic method include the use of green reducing agents, environmentally benign solvents and no inert atmosphere is required. The resulting CuO NPs are characterized by UV-Visible spectroscopy, XRD, XPS, HRTEM, and FESEM. These nanocubic and nanoflake-like morphologies for CuO NPs had a controllable diameter in the range of 30-100 nm. The results demonstrate that maintain and of pH is important for the formation of the CuO NPs. The resulting CuO NPs exhibit more antibacterial activity.