Abstract: The technology of hydraulic pulsed cavitating-j et has demonstrated in conventional wellhole field application that it can improve ROP(Rate of Penetration)significantly.Therefore, for economically developing offshore oil and gas resources in marginal regions,combining slim-hole single-channel well and the ROP improving technology of hydraulic pulsed cavitating-jet,a small-size(outside diameter:120mm)hydraulic pulsed cavitating-jet generator has been devel-oped.In order to figure out its jet characteristics,we have made a research by laboratory experi-ment on its parameters of pulsed frequency,the inlet/outlet pulsating pressure amplitude,pres-sure loss and jet characteristic of self-oscillating nozzle.The test results show that the pulsed fre-quency increases linearly with the increase of the flow rate,the inlet/outlet pulsed pressure am-plitude increases with the increase of the flow rate,the pressure loss increases quadratic curve with the increase of the flow rate.When the flow rate is 10L/s,the pulsed frequency is 8Hz,the out-let pulsed pressure amplitude is 1.2MPa and the pressure loss is 1.6MPa.The self-oscillating nozzle can bring about negative pressure and cavitation.A research on the mechanism analysis of ROP im-proving of hydraulic pulsed cavitating-jet has also been made.Its mechanism contains 2 parts:hydraulic j et can improve the efficiency of cuttings cleaning and cavitating-j et can improve the ef-ficiency of rock breaking.