In present study, boiling of water-silica nanofluids on circular flat plate heater, to investigate the variation of heater surface and characteristics of nanofluid boiling at periods of time was carried out. The experiments were performed by focusing on surface topology. Concentration of nanofluid was between 0-0.01 vol. %. Results showed that BHTC increases with nanofluid concentration and indicated the optimal amount for 0.007 vol. %. The CHF enhancement for 0.005, 0.007 and 0.01 vol. % was 52, 67 and 87%, respectively. Evaluation of heater surface roughness showed that the surface roughness increases with concentration and time duration of boiling. Boiling of deionized water (DI) on nanocoated surfaces which created under boiling of nanofluids with low concentration at different periods of time, showed that CHF is constant while in high concentraion (0.01 vol. %), CHF increases (27%). The effect of time duration of nanofluid boiling in constant heat flux on characteristics of DI water boiling and surface roughness was investigated. Results illustrated that preparing of nanocoated surface in nuclear boiling region with 0.007 vol.%, results in enhancement of BHTC, but for 0.01 vol. %, BHTC decreases. Boiling of DI water on nanocoated surface in critical heat flux region for 0.007 vol. % ,causes to increase in CHF and decrease in BHTC. Also, analysing of surface roughness in various duration times of boiling at constant heat flux showed that with increasing boiling time, surface roughness increases. Boiling of deionized water on nanocoated surface in two regions of boiling; nuclear boiling region and critical heat flux region, indicated that CHF and BHTC was enhanced. Repeating of boiling of DI water on nanocoated surface for several cycles showed that the roughness of surface was almost constant in consecutive boiling. Keywords: Pool boiling, Nanofluid, Critical heat flux, Boiling heat transfer coefficients, Surface roughness, Periods of boiling time