The MWD transmits signals by mud pulses free from cable lines and cable cart for signal transmission and power supply. When the drill rods are connected, the down hole is not necessary to be raised, this saves times and drilling expenses. This instrument has unique advantages for orientation and angle holding. YST-48X MWD is the first domestic instrument of this kind widely applied in China. YST-48R type MWD is the upgraded type of YST-48X and its flexibility and reliability have been improved greatly, with gamma measurement added.