The biological and ecological characteristics of Amblyseius nicholsi Ehara et Lee (Acari: Phytoseiidae) were studied. The optimal relative humidity for egg hatching was 75.5–85%. Tests of 11 different plant pollens on the development, survival rate and reproduction of A. nicholsi in the laboratory showed that the mites fed different pollens exhibited different immature survival rates. The developmental times from the egg to adult stage ranged from 4.95 to 6.67 days and reproduction was the greatest for A. nicholsi fed Ricinus communis pollen, which was found to be the best pollen diet for A. nicholsi. This study provided fundamental information for mass-rearing of A. nicholsi and for enhancing the performance of A. nicholsi as a predator of citrus pests. Effects of temperature on development, survival rate and fecundity have been observed. The intrinsic rate of natural increase(r_m), net reproductive rate (R₀), finite rate of increase (λ) and time for population to double at 25°C were 0.182, 28.027, 1.199 and 3.8 respectively. These parameters indicated that A. nicholsi had short developmental time and a reproductive potential capable of building high populations in a short time. The predatory capacity of A. nicholsi on Eotetranychus kankitus showed that it is a useful biocontrol agent against the latter.