Near-bit MWD technology is one of the most promising new technologies in the field of petroleum drilling. It is characterized by near-bit geological and engineering parameter measurement while drilling， transmission， data interpretation and decision control， which can effectively improve the oil and gas zone intersection rate and reduce drilling cost. In this paper， the development and application status of near-bit measurement systems at home and abroad are introduced， and the working principle， structure composition and characteristics of the system are described. In order to meet the demand of small diameter drilling for near-bit measurement technology， the key technical problems to be solved in miniaturization design are put forward. They includes electromagnetic wave wireless communication anti-interference technology， small-diameter turbine power generation technology， downhole MEMS sensor technology， near-bit measurement data interpretation technology， etc， which provides technical basis for the research and development of small diameter near-bit measurement systems in the future.