Associative learning is a basic mechanism required for herbivorous insects to adapt to highly variable environments. In most lepidopteran species, the adult stage is the main stage responsible for host plant selection, but newly hatched larvae can also contribute to host selection by moving a short distance from their birth position to feeding parts on plants. An understanding of mechanisms underlying olfactory associative learning in larvae would be helpful in enhancing the effectiveness of natural lethal factors on early instar stages via ecological interference and provide a scientific accordance for cultivating crop varieties that cannot be easily attacked by the larvae. Studies on olfactory associative learning in lepidopteran species have generally concentrated on the adult stage; little attention has been paid to early-instar larvae, probably because of their limited mobility and relatively simple life behaviors. Once the larvae are forced to leave their natal host plant, they need to move to plants with an odor profile that is similar to that of the previous host so that the larvae do not have to re-adapt to novel diet items and save the cost of physiological metabolism caused by host switch. As long as the memory of some key and stable cues is formed, the larvae can recognize and re-locate to these food plants, thus improving their fitness. Since the females of Helicoverpa armigera (Hübner) prefer to oviposit on or near the flowering parts of a plant and the larvae exclusively feed on flowering parts, we hypothesized that some key floral volatiles may represent the characteristic olfactory cues of their natural foods. In previous studies on larval classical conditioning, the subjects were starved enough time to enhance their feeding motivation, and the inter-stimulus intervals and inter-trial intervals were strictly controlled in the laboratory; thus, the ecological relevance of larval classical conditioning is weak. In this paper, we have reported the associative learning capability of and corresponding temporal pattern of learning performance in early-instar larvae of H. armigera (Hübner) (Lepidoptera: Noctuidae) to the association between conditioned stimuli (seven floral volatiles with biological meaning to H. armigera) and an un-conditioned stimulus (artificial diet). During a seven-day conditioning period, the larvae were continually exposed to the floral volatiles. Results of the conditioning show that the phenylacetaldehyde-conditioning group exhibited significant preference to phenylacetaldehyde. Phenethylalcohol- and linalool-conditioned groups exhibited significant preference to the corresponding conditioned stimuli. However, benzaldehyde, phenylmethanol, benzyl acetate, and geraniol did not produce a positive result at any conditioning time lengths; this suggested that the larvae selectively sensed and remembered the cue of some stable and key components during the feeding process, rather than responding to all the floral volatiles equally. In addition, the naïve group did not show any preference to phenylacetaldehyde in all the tests, regardless of the time length after 24 h of feeding; this suggested that the alteration of the olfactory preference during conditioning was not induced by physiological maturity. Taken together, H. armigera larvae exhibited olfactory learning capability, and the variation in olfactory preference had no relationship with the conditioning time length. Possible explanations for such findings have been discussed with respect to the ecological habits of the larvae.