Abstract: Environmental condition changes will alter the response relationship between ρ(Chla) and the environmental factors in lakes. With the low-pass sequential filtering trajectory method, the turning point of the response relationship between ρ(Chla) and environmental factors with time can be easily identified, and the long time series data can be segmented to establish the piecewise regression function, which provides a new perspective for studying the causal effect relationship between the environmental factors and ρ(Chla) in lakes. Taking Taihu Lake as an example, the change process of ρ(Chla) and nutrients ρ(TN), ρ(TP) and the ratio of nitrogen to phosphorus (ρ(TN)/ρ(TP)) in Taihu Lake from 2001 to 2018 was evaluated by using using a low-pass sequential filtering trajectory method. The effects of annual average temperature, nitrogen to phosphorus ratio and retention time on algae production efficiency (ρ(Chla)/ρ(TP)) were studied. The results showed that: (1) 2006 and 2011 were the two turning points of the nutrient process trajectory in Taihu Lake, and the eutrophication process trajectory of Taihu Lake was divided into three stages: the first stage was pollution stage (2001-2006), and ρ(TN), ρ(TP) and ρ(Chla) increased synchronously, reaching the first peak in 2006; the second stage was the restoration stage (2006-2011), and the concentrations of ρ(TN), ρ(TP) and ρ(Chla) in Taihu Lake were concentrated; the third stage was the stage of eutrophication aggravation (2011-2018), while the ρ(TP) and ρ(Chla) increased synchronously, and there is no turning point so far. (2) The limiting nutrient for algae growth in Taihu Lake was ρ(TP). After 2011, the nitrogen to phosphorus ratio became suitable for algae growth, which provided conditions for the outbreak of cyanobacteria. (3) From 2011 to 2018, the efficiency of algae production increased by 51%, and it is still increasing with no sign of leveling off. The increased air temperature maybe the main reason for the increase of algae production efficiency. (4) According to the prediction of ρ(Chla)-ρ(TP) function based on the filter values from 2011 to 2018, the ρ(TP) in Taihu Lake should be controlled below 52 μg/L to control the outbreak of algae bloom. (5) Since 2006, the residence time of Taihu Lake presented a decreasing trend, which inhibited the algae growth. However, the retention time was not the key factor affecting the algae production efficiency. Research showed that since 2006, a series of ecological restoration projects have been carried out in the Taihu Lake Basin, and the lake nitrogen concentration has been significantly reduced. However, due to the large amounts of nitrogen and phosphorus discharges from the basin and high concentration of phosphorus accumulated in lake sediments, the nutrient level in the water column has not been reduced to the level that can significantly inhibit algal growth. Presently, the air temperature increase trend still continues, and the algae control is still in a severe situation. In order to get rid of the decisive effect of climate warming on cyanobacteria blooms, phosphorus control should be strengthened on the basis of nitrogen control, and various measures such as hydrological regulation, bioremediation, and algae salvage should be given more considerations.