Abstract: Measurement While Drilling (MWD), Logging While Drilling (LWD) and advanced logging instruments is the important components of the international drilling high technique. The application of these high technology productions can improve the engineering controlling capability and the formation evaluation capability of extended-well and high difficulty horizontal well, and improve the drilling meeting efficiency of oil reservoirs. This paper will introduce the MWD in detail, including its measuring principle, basic construction, transmission channel, collecting instrument, downhole power, surface system, application method etc. It also introduces typical structure and function of several geological parameter measurement sensors and logging sensors in LWD at the former base. Knowing, understanding and mastering the function, characteristic and typical structure of MWD/LWD systems is important for properly usage and inventing these high and new technology instruments.