[Objectives]  To clarify the effect of density on the population growth of Phenacoccus solenopsis to improve control of this pest. [Methods]  The development and reproduction of P. solenopsis kept at (26 ± 1) ℃, a RH of 70% ± 10% and a photoperiod of 16L︰8D, was measured at different nymphal densities (2, 5, 10, 15, and 20 per 15 cm²). [Results]  The developmental duration was significantly shorter, (26.60 ± 0.57) d and (26.67 ± 0.45) d, respectively, at nymphal densities of 5 or 10 per 15 cm² (P < 0.05). Female fecundity was highest [(100.56 ± 1.25) progeny per female] at a nymphal density of 2, followed by a nymphal density of 5 [(61.29 ± 2.64) progeny per female]. The survival rate at a nymphal density of 5 was 75%, which was significantly higher than the other treatments (P < 0.05). The net reproductive rate (R₀) was highest at a nymphal density of 2 (31.425), followed by that at a nymphal density of 5 (22.985). R₀ decreased with increasing nymph density. The population doubling time (t) was shortest at a nymphal density of 5 (5.635 d), followed by a nymphal density of 10 (105.682 d). The t value was first negatively, then positively, correlated with nymphal density. [Conclusion]  Nymphal density affects the population growth of P. solenopsis. A density of 5 nymphs / 15 cm² was the most suitable for the growth, development and reproduction of this species; lower or higher densities were less suitable. These findings are useful for further research on control methods for P. solenopsis.