Huangtai algal blooms are key indicators of eutrophication and lake-ecosystem damage. Understanding the spatiotemporal heterogeneity of their growth is critical for preserving the ecological environment. The dimidiate pixel model is commonly used to estimate vegetation coverage; however, indices such as the normalized difference vegetation index have not been specifically constructed for the Huangtai algae spectrum and thus are not specific or sufficiently precise for use as indicators. Therefore, we propose a new dimidiate pixel model based on a novel additive vegetation index to calculate the Huangtai algal coverage for each pixel using Landsat multispectral satellite images with 30-m resolution. The results showed that the additive vegetation index with R