A miniature electroacoustic transducer includes: a metal shell, having the shape of a barrel with one open end; a vibrating system, including a vibrating diaphragm and a voice coil; and a magnetic circuit system, including a concentrating flux plate, a magnet and a magnetic yoke that are sequentially combined together. The magnetic circuit system is formed with a magnetic gap corresponding to the voice coil; the vibrating system and the magnetic circuit system are fixedly installed in the barrel-shaped shell; the components in the structure are further modularized, maximizing the magnet under the same product dimension and effectively improving the product sensitivity. An assembling method of the electroacoustic transducer includes: a. providing a barrel-shaped metal shell with one open end; b. putting a pre-assembled vibrating system into the shell; c. putting a pre-assembled magnetic circuit system into the shell; and d. fixedly assembling the shell with the magnetic yoke.