This book introduces the downhole engineering cybernetics—a new subdiscipline focusing on the downhole control engineering of oil and gas wells by using the principles and methods of engineering cybernetics. It covers four main parts: ① theoretical basis—downhole system dynamics, control signal analysis; ② technological basis—design of downhole control mechanism, downhole parameter acquisition, and transmission technology; ③ laboratory construction and experimental methods; ④ product development—downhole control systems and tools. This book is a valuable reference both for researchers and engineers in the relevant fields.