Shedding of cloud cavitation in a diesel nozzle is a common phenomenon of cavitation instability which has a great influence on erosion damage and spray atomization process,but it hasnt been studied in details and the mechanism remains unclear.In this paper,visualization experiments and Large Eddy Simulation(LES)were carried out to study the process of periodic cloud cavitation shedding and re-entrant jet happened in a 2mmwidth nozzle with fuel of diesel.Numerical experimental images provide a better insight into this physical mechanism.The results show that cavitation inception is formed at the edge of inlet and the recirculation zone which below the shear layer.Then the attached cavitation grows and shedding of cloud cavitation occurs due to the re-entrant jet located between cavity and wall.Moreover,the dynamic mechanism causing shedding of cloud cavitation is a combination of shedding vortex.Cavitation shedding frequency of about 2600Hz is get by measuring the fluctuation of cavitation length.As a result,inception of cavitation,re-entrant jet and cavitation cloud shedding are accurately predicted by LES in accordance with the quantitative images observed in the experiment.