【Aim】To determine the primary overwintering stages of the invasive mealybug Phenacoccus solenopsis, cold hardiness and differential responses of key cryoprotectants and metabolites in different developmental stages were assessed. The aim is to provide a theoretical basis for monitoring and regional management of this pest.【Method】The developmental duration and survival time of P. solenopsis were recorded under a temperature gradient (4, 10, 16, 22, and 28 ℃). The supercooling point (SCP), freezing point (FP), and content of cryoprotectants (proteins, glycerol, trehalose, sorbitol, and free fatty acids) were measured.【Result】Pseudopupae, third-instar nymphs, and adult females exhibited strong cold hardiness. Pseudopupae displayed the highest supercooling capacity, with the lowest mean SCP (-24.86 ℃) and FP (-21.18 ℃) at 16 ℃. Third-instar nymphs resisted low temperatures mainly by extensive accumulation of cryoprotectants, with the content of proteins (148.75 mg·g^-1) and glycerol (2 497.57 μmol·g^-1) being the highest compared with that of other stages at 16 ℃. Although with slightly lower supercooling capacity, adult females had the highest sorbitol content (1.54 mg·g^-1) at 16 ℃ and survived for the longest periods (41.70 and 9.80 d, respectively) at 10 and 4 ℃, demonstrating exceptional long-term cold hardiness. Moreover, the water content in the three stages remained relatively stable under low temperatures.【Conclusion】This study reveals the differences in cold hardiness and the related physiological indicators among different developmental stages of P. solenopsis, providing a theoretical basis for invasion risk prediction across different climatic zones.