[Objectives]  To investigate the ovarian development and timing of oviposition in the Goji fruit fly, Neoceratitis asiatica (Becker), an important pest of Lycium barbarum L, and thereby identify the critical period for controlling this pest in the field. [Methods]  Females were dissected under a microscope 1 to 45 days after their emergence and the length and width of their ovaries, and the number of mature eggs, were recorded. In addition, the number of eggs laid on young fruits within 45 days of emergence was recorded to determine the timing of oviposition. [Results]  Ovarian development could be divided into five stages; the early stage (Ⅰ), the egg-maturing stage (Ⅱ), the early oviparous stage (Ⅲ), the peak oviparous stage (Ⅳ), and the late oviparous stage (Ⅴ). Females became sexually mature on the fourth day after eclosion and those that had mated began laying eggs on the same day. [Conclusion]  The fourth day after the emergence of female N. asiatica is the critical time for controlling this pest in the field.