Summary: This paper aims to examine how using lattice Boltzmann method (LBM) aids the study of the isothermal-gas flow with slight rarefaction in long microtubes. A revised axisymmetric lattice Boltzmann model is proposed to simulate the flow in microtubes. The wall boundary condition combining the bounce-back and specular-reflection schemes is used to capture the slip velocity on the wall. Appropriate relation between the Knudsen number and relax-time constant is defined. The computed-slip velocity, average velocity and non-linear pressure distribution along the microtube are in excellent agreement with analytical solution of the weakly compressible Navier-Stokes equations. The calculated-friction factors are also consistent with available experimental data. For simulations of slip flow in microtube, LBM is more accurate and efficient than DSMC method. The laminar flow in circular microtube is assumed to be axisymmetric. The present LBM is only applied to the simulation of slip flows (0.01?<?Kn0<0.1) in microtube. Lattice-BGK method is a very useful tool to investigate the micro slip flows. A revised axisymmetric D2Q9 lattice Boltzmann model is proposed to simulate the slip flow in axisymmetric microtubes.