Indoor farming system has played an important role in precision agriculture. In recent years, many innovative greenhouses have been built in China. In order to enhance the thermal insulation of multi-span greenhouses in northern region, external thermal screen has been installed on multi-span greenhouses (Shouguang-type intelligent greenhouses). The external thermal screen and its power mechanism were installed above a large gutter. However, the larger gutter caused the lower light intensity in the greenhouse. In order to analyze the indoor light environment and optimize the gutter and greenhouse design, a dynamic model of light distribution inside the greenhouse was constructed. Based on the model, the uniformity and sensitivity of indoor light environment were analyzed. The results showed that the order of the influence on the average value of daily accumulated radiation in the cultivation area was the gutter distance, width, depth and height. Among different design combinations, there were multiple optimal ones of light distribution in the cultivation area. And the current gutter design of Shouguang type greenhouse was reasonable for uniform indoor light environment on local winter solstice day, including the distance (12.00m), and width (1.60m), depth (0.86m) and height (6.30m) of single gutter. According to the simulation results under different scenarios, the suitable ratios of the sum of gutter height and depth over the sum of gutter distance and width among all the suitable designs (the minimum variation coefficient of radiation intensity) were between 0.49 and 0.54. The dynamic model could provide a theoretical basis for the design and application of Shouguang-type intelligent greenhouses in different regions.