This paper is concerned about mechanism of outstanding CHF enhancement phenomena using nanofluids, a subject with academically and industrially remarkable interest. Pool boiling experiments using an electrically heated horizontal wire were carried out with various water-based nanofluids containing Ag, Al2O3, SiO2, and TiO2 nanoparticles. The results showed that nanoparticle deposition on the heater surface occurred during pool boiling of nanofluids, and that the effect of nanoparticle porous layer on CHF could explain enough the CHF enhancement of nanofluids. Then the porous surface was characterized using surface wettability and capillary wicking performance, which are the significant properties of boiling surface influencing CHF. Discussion of the results suggested that the outstandingly enhanced CHF performances of nanofluids under the nucleate pool boiling were associated with enhanced surface wettability and liquid suction effect due to capillary wicking on the nanoparticle-deposited surface.