The utility model discloses a tension releasing device and position collocation, which is mainly used on sewing machine. The tension of yarn can be released timely and a proper tension releasing device and position collocation can be offered by the utility model. The automatic tension releasing device includes a yarn connecting unit, a power supply device and a linkage mechanism. The yarn connecting unit is arranged at the back of the top of the sewing machine; the power supply device is arranged at the back of the sewing machine; the linkage mechanism is connected with the yarn connecting unit and the power supply device. The working principle of the utility model is that: firstly, a yarn gripping implement of the yarn connecting unit loosens a gripping piece, and then making use of a yarn hitching implement to release tension, when the yarn hitching implement is arranged at the first position, the yarn hitching implement does not produce a displacement and the yarn can not be drawn to move; and when the yarn hitching implement is driven by the power supply device and arrive at the second position, the yarn can be drawn to move because of the displacement of the yarn hitching implement; and thus the yarn hitching implement returns to the first position so as to loosen yarn.