The invention relates to a device and method for promoting interaction of fine particles in smoke of a coal-fired boiler.The device is characterized by comprising a rectangular channel, a shrinking and expanding throat, a turbulence clustering chamber and a smoke outlet, the rectangular channel serves as a smoke inlet, the shrinking and expanding throat comprises a gradually-shrinking part and a gradually-expanding part, the gradually-shrinking part is connected with the rectangular channel, the gradually-expanding part is connected with one end of the turbulence clustering chamber, and the smoke outlet is formed in the other end of the turbulence clustering chamber and connected with a subsequent dust removing device; a plurality of rectangular fins are arranged in the turbulence clustering chamber, every two rectangular fins form a set, n sets of fins are arranged, n is larger than or equal to 2, the two rectangular fins of each set are in a splay shape, the small opening end of the splay shape faces the smoke flow incoming direction, and the n sets of rectangular fins are sequentially arranged in the turbulence clustering chamber in the smoke flow incoming direction; an included angle ranging from 20 degrees to 60 degrees is formed between the rectangular fins and the smoke flow incoming direction, and the proportion of the length, in the width direction, of the turbulence clustering chamber to the diameter of the throat part of the shrinking and expanding throat is 6:5.