The invention discloses a method for synthesizing a flower-ball-shaped 
bismuth phosphate nano-
powder photocatalyst by a 
microwave hydrothermal process. According to the key points of the technical scheme, the method comprises the following steps: (1) preparing a 
bismuth nitrate solution from 
bismuth nitrate and deionized water, and adding an 
ionic liquid 1-butyl-3-methylimidazole 
hexafluorophosphate in the 
bismuth nitrate solution under a stirring condition, thereby forming a uniform transparent solution; (2) transferring the uniform transparent solution into a 
hydrothermal reaction kettle, adjusting the pH of the reacting solution to 1-11 by acid or alkali, placing the 
hydrothermal reaction kettle into a 
microwave digester and lasting 
microwave reaction for 10-60 minutes; and (3) after reaction, cooling, centrifuging, washing and 
drying, thereby obtaining the flower-ball-shaped 
bismuth phosphate nano-
powder photocatalyst. According to the method, the 
ionic liquid serves as a substitute for a traditional 
raw material to prepare the BiPO4 photocatalyst; in a 
reaction system, the 
ionic liquid can not only serve as a 
raw material, but also serve as a template agent for modification on the surface of BiPO4, and is capable of capturing photogenerated electrons and inhibiting the recombination of photogenerated electrons and 
electron holes, thereby enhancing the capability of 
bismuth phosphate in photocatalytically degrading organic pollutants.