[Aim] In order to provide scientific reference for the risk assessment and host adaptation of cotton mealybug, Phenacoccus solenopsis Tinsley, the effects of host plants on body size and energy substances contents of adult females P. solenopsis were studied.[Method] After having reared five generations of P. solenopsis in the lab with eight different host plants, body length, body width, body weight and energy substances contents (lipid, soluble proteins, soluble sugar) of 7-day-old adult females were measured.[Result] After feeding on different host plants, there were significant differences in body size and energy substances contents of adult females P. solenopsis. After feeding on potato, adult female body length was 4.80 mm, adult female body width was 3.07 mm, and adult female body weight was 7.11 mg. These body size parameters were significantly higher than for females fed on the other host plants. After feeding on cotton (Bt cotton and conventional cotton), the soluble protein content in adult females P. solenopsis was the highest (58.77 and 57.70 mg·g^-1). After feeding on conventional cotton, the soluble sugar content was the highest (75.02 mg·g^-1). After feeding on potato, the lipid content was the highest (349.00 mg·g^-1).[Conclusion] Host plant significantly affected the body size and energy substances contents of adult females P. solenopsis. After feeding on potato, adult females P. solenopsis have larger body size and higher body energy substances contents. Therefore, the population monitoring of P. solenopsis on potato should be strengthened.