Growth of pearl oysters, Pinctada martensii was studied from June 2003 to March 2005 in Li'an Lagoon of Hainan Island in China. Shell height (SH) and total weight (TW) were measured monthly and temperature was recorded daily. The growth of oysters is characterized by fast initial growth of SH in the first year, followed by rapid increase of TW in the second year. Growth of SH was influenced by temperature, showing reduced growth rate in summer, fitting the extended Von Bertalanffy model: y = 92.99(1 - e^{(-0.002070(t-13.63) 0.04164 sin(2π/365.25)(t-193.03))}) (y: SH in mm, t: time in day). Growth rate of total weight increased steadily, except during typhoons or spawning, fitting the logistic model: y = 53.63/(1 e^{-0.009770(t-463.33) 0.1938 sin(2π/365.25)(t-564.73)}) (y: TW in g, t: time in day). It is also established that in Hainan, most oysters were mature and suitable for pearl nucleus insertion after 16–20 mo of farming; hence to meet the implantation season in April to June, it is more advisable to conduct hatchery operation in autumn than in spring.