In this paper, the nonlinear free vibration responses of functionally graded nanocomposite fluid-conveying tube reinforced by single-walled carbon nanotubes (SWNTs) in thermal environment is investigated. The SWCNTs gradient distributed in the thickness direction of the tube forms different reinforcement patterns. The materials properties of the functionally graded carbon nanotube-reinforced composites (FG-CNTRC) are estimated by rule of mixture. A higher-order shear deformation theory and Hamilton’s variational principle are employed to derive the motion equations incorporating the thermal and fluid effects. A two-step perturbation method is implemented to obtain the closed-form asymptotic solution for these nonlinear partial differential equations. The nonlinear frequency under several patterns of reinforcement are presented and discussed. We conducted a series of studies aimed at revealing the effects of the flow velocity, environment temperature, geometrical ratios and carbon nanotube volume fraction on the nature frequency.