The invention discloses a synthesis method for aromatic hydrazine sulfate. The synthesis method includes the steps that firstly, aromatic amine is added in sulfuric acid with the mass fraction ranging from 15% to 65%, the temperature is lowered to -5-15 DEG C, a diazotization reagent is dropwise added in the reaction liquid, and diazonium salt is obtained after reaction; secondly, a reducing agent is prepared into a solution, a reducing solution is obtained, the diazonium salt obtained in the first step is dropwise added in the reducing solution, heating reduction is conducted after drop-by-drop addition is completed, and reducing material liquid is obtained through filtration; and thirdly, the reducing material liquid obtained in the second step is heated, dilute sulphuric acid is dropwise added in the reducing material liquid to conduct the acidolysis reaction, the temperature is lowered after the reaction is finished, the aromatic hydrazine sulfate is separated out, a filter cake and filtrate are obtained through filtration, the filter cake is washed with dilute sulphuric acid, and an aromatic hydrazine sulfate product is obtained, and sodium sulfate salt is recycled after the filtrate is preprocessed. Compared with a traditional process, the obtained aromatic hydrazine sulfate is high in yield and purity, the purity reaches 97% or above, the yield is higher than 91%, salt in the wastewater obtained through the reaction is the simplex sodium sulfate salt, and the recycling value is high.