A heat pipe (20) includes a pipe (21), a wick (22), and an operating fluid. The wick is a capillary structure including a carbon nanotube layer, and is fixed to an inside wall of the pipe. The operating fluid is sealed in the pipe and soaks into the wick. The operating fluid includes a pure liquid, and a plurality of nanometer-scale particles uniformly suspended in the pure liquid. The nanometer-scale particles can be carbon nanocapsules (30) or particles of a metal (32) with high thermal conductivity. Each carbon nanocapsule can further have a metal with high thermal conductivity filled therein. The carbon nanotube layer contains carbon nanotubes of small size and high thermal conductivity, therefore the capillary performance of the wick is good. Further, because the operating fluid includes nanometer-scale particles with high thermal conductivity, this ensures that the operating fluid has high thermal conductivity.