The invention discloses a piston with a combustion chamber in a dual-fuel engine (combustion chamber type piston (1)). The piston with the combustion chamber in the dual-fuel engine is aimed to overcome the disadvantage that natural gas burns incompletely due to over-high HC emission of a natural gas/diesel dual-fuel engine under small load. An eight-petal dumbbell-shaped combustion chamber is arranged at the top end of the combustion chamber type piston (1), and the eight-petal dumbbell-shaped combustion chamber is co-linear with the symmetrical axis of the combustion chamber type piston (1); the eight-petal dumbbell-shaped combustion chamber is composed of an upper eight-petal-shaped column body hole (2), a lower dumbbell-shaped rotary chamber (3) and a transitional circular curved surface (4) in a connecting mode. The eight-petal-shaped column body hole (2) is composed of eight equal-radius inner cylindrical surfaces which protrude towards the inside and eight equal-radius outer cylindrical surfaces which protrude towards the outside, the eight inner cylindrical surfaces and eight outer cylindrical surfaces are arranged alternately, the dumbbell-shaped rotary chamber (3) is composed of an outer circular arc surface, a convex circular table surface and a bottom circular arc surface, and the convex circular table surface is located at the center of the dumbbell-shaped rotary chamber (3) in the eight-petal dumbbell-shaped combustion chamber.