Abstract: This paper deals with the pulse signal transmission mode for drilling fluids in measurement while drilling (MWD) systems. According to the fluid mechanics principles, the fundamental study on the waterhammer problem of non?Newtonian fluids in the signal transmission system of MWD was deeply investigated. A linear processing method and approximate expression of the differential viscosity for power?law fluids were proposed. The linear momentum balance equations with variable coefficients for the perturbed variables of transientflow of power?law fluids were presented. On the basis of this, the waterhammer equations of the power?law fluids were set up. The results showed that the solutions of transient flow problems for power?law fluids are not only related to the fluids nature, but also depended on flowing state of steady flows. The variable coefficients of the equations showed the main difference between Newtonian and non?Newtonian fluids transient flow. In this paper, the highlights of waterhammer equations for power?law fluids compared to the existing theories can be summarized: the study considers the behavior of the non?Newtonian fluids, and the solution is strictly analytical, so it need not be calculated through the empirical coefficients of Darcy?Weisbach. The proposed theory and evaluation method make up current deficiencies of the waterhammer theory for non?Newtonian fluids. The established theory in this paper provides the basis for the dynamic analysis of drilling fluid pulse signal transmission in MWD systems