The invention discloses a synthesis method of a 
prulifloxacin key intermediate. The 
prulifloxacin key intermediate is 7-chloro-6-fluoro-1-methyl-4-oxo-1H,4H-[1,3]thiazolo[3,2-a]
quinoline-3-
carboxylic acid ethyl ester (I), the synthesis method comprises the following steps: taking 1-(4-chloro-2,5-difluorophenyl)ethanone (II) as an initial 
raw material, carrying out 
Claisen condensation to obtain a compound (III), carrying out ethylation on the compound (III) to obtain a compound (IV), carrying out ammonolysis on the compound (IV) and an ammoniation 
reagent, carrying out cyclization reaction under the action of 
potassium carbonate to obtain a compound (VI), carrying out hydroxyl protection on the compound (VI) by using 
acetyl chloride to obtain a compound (VII), carrying out chlorination reaction on the compound (VII) and a chlorination 
reagent, and then performing cyclization reaction under the action of 
sodium acetate to obtain an intermediate target product. The synthesis method disclosed by the invention has the characteristics of simple process, simplicity and convenience in operation, mild 
reaction conditions, avoidance of use of toxic and harmful reagents, reduction of environmental 
pollution, higher total yield and the like, thereby having higher implementation value and social and 
economic benefits.