The velocity of the fluid in every location of the water jacket has a direct relation with the rate of heat transfer. Approximately one-third of fuel heat release in an IC engine is lost to the environment by coolant flow. So, it is necessary to determine the velocity of coolant according to the rate of heat transfer. The water jacket of an engine has complex and non-transparent geometry and it is impossible to measure velocity in each location. In this paper, the velocity of coolant is measured in a transparent water-jacket of the EF7 engine with the PIV method. A volumetric flow rate of coolant is determined according to engine speed that two engine speeds considered in this research. In the PIV method with the dispersion of special submerged particles in coolant on a transparent water jacket and shining of the laser beam to particles, it is possible to track them. Then, with image processing, velocity vectors are carried out with the toolbox of the Matlab program. Extraction of results of the can is used for the study of fluid behavior. Besides experimental work, simulation with Fluent software was done for comparison between results.