This study numerically investigates the electroosmotic flow and heat transfer in a wavy surface of the microtubes. The solution takes the electrokinetic effect and the amplitude of the wavy surface into consideration. A simple coordinate transformation method is used to transform a complex wavy micro-tube into a regular, circular tube. The governing equations, including the Poisson-Boltzmann equation, the modified Navier-Stokes equations, and the energy equation with their corresponding boundary conditions are also transformed into the computational domain and then solved by the finite difference method. The main objective is to investigate the difference of fluid flow and temperature fields for various wavelength ratio a and the electrokinetic parameter Ξ². Results show that the distributions of the skin-friction coefficient and the local Nusselt number are oscillatory along the stream-wise direction for the wavy micro-tube (a β 0). The amplitude of the oscillated local Nusselt number increases with an increase in the electrokinetic parameter Ξ² and wavelength ratio a, but that of the skin-friction coefficient decreases with an increase in the electrokinetic parameter Ξ². The heat transfer enhancement is significant for the larger electrokinetic parameter Ξ² and wavelength ratio a.