The main objective of this work is to investigate pasteurization of caw's milk by laser and its effect on Milk's pH. In this pilot study, Nd: YAG laser was used to irradiate raw cow's milk in order to kill bacteria and fungi; then its effect on the milk's pH has been studied. Six samples of cow's milk were taken from the farm directly, without any additions of preservatives, five of these six samples were treated with Nd: YAG laser (1064 nm) using different output powers specifically (10, 20, 30, 40 and 50) Watts for two minutes and the sixth sample was left without irradiation as a control. Samples were then analyzed for surviving bacteria and fungi. The results revealed that complete sterilization of bacteria and fungi was achieved using maximum output laser power 50 W for two minutes. During this experiment it was found that the pH of milk was reduced from 6.18 for the control sample in the first day down to 4.50 for the highest laser-treated sample after five days.