Abstract: Volcanic rocks existed in the study area of oil and gas field in the East China Sea. In view of volcanic rocks magnetic characteristics, based on the total magnetic anomalies △T results, using the technique of reducing to the pole by variable inclination for the total magnetic anomalies △T and technique of wavelet multiscale decomposition analysis, distribution and thickness of the volcanic rocks had been studied in the area. With necessary conditions for physical properties and scale distribution of magnetic bodies in development of oil and gas fields, to study distribution of the magnetic bodies is feasible using magnetic survey results.