Firstly, Gemini imidazoline quaternary ammonium was prepared with butyl amine and epoxy chloropropane and long chain imidazoline. And the structure of the synthesized product was characterized by FTIR and HNMR. Then, emulsified asphalt was made by the Gemini imidazoline quaternary ammonium and Qin huangdao AH-70 asphalt and the preparation conditions of emulsified asphalt was investigated. In addition, the economic benefit of Gemini imidazoline quaternary ammonium was analyzed. The results show that the optimal conditions were as follows: pH value was 5.0, the asphalt temperature was 135℃, the soap liquid temperature was 55℃, the mass ratio of water and oil was 6:4, and emulsifier dosage was 1.5%.