The ovipositing preference of Helicoverpa assulta Guenée to Nicotiania rustica was much higher than that to Nicotiania tabacum. In order to identify the influence of host selection preference of parental adults on the population growth of later generations, the effects of the two tobacco species on the growth development and survivorship, food utilization and conversion, as well as population dynamics of Helicoverpa assulta Guenée under experimental and natural conditions, respectively, were studied by the life-table method. The results showed that: (1) When reared on N. rustica, under laboratory conditions with (26±1)℃, (75±5)% relative humidity and 16L∶8D photoperiod, the development duration of H. assulta larvae significantly prolonged, while the survival rate of each stage of larvae from 1st to 3rd instar and the fecundity of female adults reduced notablely, and the net reproductive rate (R0=16.1086) and innate capacity of increase (rm=00848) decreased. (2) There were no significant differences in the relative consumption rate (RCR) and approximate digestibility (AD) between the 6th instar larvae reared with two tobacco species. Compared to the larvae feeding on N. tabacum, the relative growth rate (RGR), efficiency conversation of ingestion (ECI) and digestion (ECD) of larvae on N. rustica significantly decreased. (3) The 2nd generation population of H. assulta in N. tabacum tobacco field (I=19922＞1) increased but declined in N. rustica tobacco field (I=0.6577＜1), the increase of the 3rd generation population slowed down in both two tobacco fields, while the population increasing was faster in N. tabacum field (I=04571) than in N. rustica field (I=0.3592). These results indicated that N. rustica plant was comparatively not suitable for the population increase and reproduction of H. assulta, therefore its host suitability was lower than N. rustica.