A pressure-actuated rocket system comprises a bottom base, a detonator and a rocket body. A top base is placed on a top surface of the bottom base. At least one through hole is located on a side of the top base and extended to an opening of the top surface. The hollow detonator has a closed and an opened ends. The rocket body is a bottle with fins. After soda powder is placed inside the detonator and vinegar is filled into the rocket body, the bottom base, the detonator and the rocket body are held inclined. The openings are aimed at the inclined bottom base in turn, the pressure-actuated rocket system is then turned upside down. Soda powder subsequently falls and reacts with vinegar, and gas is generated. A pressure accumulates inside the rocket body until it is high enough to shoot the rocket body up.