Abstract  [Aim]  To determine the spatial distribution patterns of eggs and larvae of Tuta absoluta in greenhouses and open fields, develop optimal theoretical, sequential, sampling models to improve the precision of monitoring, occurrence prediction, prevention, and control measures for this pest. [Methods]  Surveys were conducted in 2023 in tomato growing areas in Yinchuan and Shizuishan, Ningxia. The interlaced and five-point sampling methods were used to assess the density of T. absoluta. Data analysis was performed using an aggregation index and the Iwao regression model, leading to the establishment of theoretical sampling models and sequential sampling models. [Results]  Based on the diffusion coefficient, the negative binomial distribution K index, diffusion index, clumping index, and mean crowding of the eggs and larvae in both greenhouse and open field conditions, our findings demonstrate an aggregation distribution pattern. Specifically, we observed a mean aggregation number (λ) greater than 2 in the greenhouse environment while λ was less than 2 in the open field. Linear regression equations were derived as m^* = 4.01 + 0.46m and m^* = 2.11 + 0.93m for eggs and larvae in the greenhouse respectively; whereas for open field samples, the equations were m^* = 2.00 + 2.75m and m^* =7.38 + 0.48m for eggs and larvae respectively. [Conclusion]  The results revealed that the eggs and larvae of T. absoluta had an aggregated distribution in both greenhouses and open fields. For an egg density of 2 eggs per leaf in open fields or greenhouses, we recommend sampling 310 or 190 specimens, respectively, whereas for a larval density of two per leaf, we recommend sampling 350 or 140 specimens, respectively.