This book systematically discusses the data transmission modes, implementation principles, and simulation and field test of Measurement While Drilling communication system, and its application at home and abroad. The advantages and disadvantages of different transmission modes and the limitations in application are analyzed, followed by the outlook for data transmission technology of MWD and its future direction and development trend. The main contents of this book include: an introduction to the data transmission technology in MWD; the data transmission techniques in cable drilled logging, especially the application and tests of OFDM (orthogonal frequency division multiplexing) in cable logging; the mud pulse transmission technology in drilled logging with emphasis on the theoretical derivation and experimental scheme of the continuous waves transmission; an encoding method of MWD data based on the mud pulse transmission and compression perception; the theoretical derivation and experimental scheme of data transmission by electromagnetic waves in MWD, especially eliminating interference signal algorithm of EM-MWD; the theoretical analysis and practical application of acoustic transmission of data in drilling with emphasis on the acoustic NC-OFDM transmission. This book pays attention to the combination of theory and practice, containing both the derivation of theoretical formulas and the results of simulation and field tests. It can be used as a reference book for MWD researchers and people interested in this field.