The invention discloses a water quality ameliorant for pond culture turtle and a water quality improvement method, and belongs to the technical field of the aquaculture. The water quality ameliorant is formed by 18.2-20% of photosynthetic bacteria stoste, 0.4-1% of photosynthetic bacteria culture medium, 0.3-0.6 of yeast extractive, 1.5-1.7% of salt, 0.01-0.02% of selenium and the balance of water. The mode of applying on the bottom of the pond is used, the turtle amount and water volume in the pond are combined, and the application frequency and the application amount of the water quality ameliorant are rationally controlled, so not only the water quality condition can be effectively improved, the generation of the harmful bacteria is inhibited, and the oxygen content in the water is improved, but also the turtle diseases can be prevented, and the water quality ameliorant has special growth promoting function for the growth of the turtle.