The invention relates to a sealed small low-impact release screw bolt. The bolt comprises an inner cylinder (1), a shear pin (2), a wedge block (3), a piston (4), a sealing ring (5), a double O-shaped ring sealed baffle (6) and an outer cylinder (7). The bolt is characterized by small size, sealing type, low impact, strong connection and no pollution. Before separated, the two polars of the connected body form strong connection; and when separated, the two polars of the connected body can be safely and fast separated and generate low impact disturbance, thus the bolt is a pyrotechnic connection separating device with good comprehensive performance, and can be directly used in the stage separating systems of the missile and other spacecrafts, also provide beneficial reference for the design of the similar separating mechanism, have good application prospect.