The invention provides a self-adaptive micro-tension fast reaction device and method for core breaking protection of core yarn and a spinning machine. The device is composed of a godet roller, a swing rod, a rotating shaft, a shell body, a fixing sleeve, a ball head locating piece, a spring, a push rod and a yarn breaking ring, wherein the shell body is obliquely fixed on a rocker arm of a spinning frame through the fixing sleeve. When normal working, core wires pass through the godet roller and drive the godet roller to rotate, and the micro tension in the core wires keeps the swing rod in a state of dynamic balance. When the core wires are broken, the godet roller and the swing rod lose balance, and the swing rod moves clockwise to drive the rotating shaft to press the ball head locating piece down, so that the push rod is free of the restriction of the ball head locating piece and moves forward under the force of the spring, moreover, the yarn breaking ring connected in a front groove of the push rod is stuck in the middle of two back rollers to cut off roving, thereby rapidly stopping roving feeding, and preventing the formation of hollow yarn. Compared the prior art, the self-adaptive micro-tension fast reaction device and method for core breaking protection of core yarn and the spinning machine can stop roving feeding immediately when the core wires are broken, and thoroughly eliminate the hollow yarn and core-leakage yarn.