An electronic cigarette with oval shaped cross section, comprising a battery assembly and an outer housing of battery assembly with an oval shaped cross section, a control assembly and an outer housing of control assembly with an oval shaped cross section, a vaporization assembly and an outer housing of vaporization assembly with an oval shaped cross section, and a mouthpiece with an oval shaped cross section, an inner housing of vaporization assembly is arranged inside the outer housing of vaporization assembly and is sleeved on the vaporization assembly, wherein the vaporization assembly comprises a vaporizer and an e-cigarette liquid cup, wherein an outer wall of the vaporizer is in close fit with an inner wall of the inner housing of vaporization assembly, and a space is formed between an outer wall of the e-cigarette liquid cup and the inner wall of the inner housing of vaporization assembly to serve as a vapor flow channel; the inner housing of vaporization assembly is arranged with a vapor flow outlet at one end, characterized in that: the outer edge of the vapor flow outlet is hermetically connected with a bell-mouth structure, which is formed on the mouthpiece and is made of soft material, in a manner of being pressed against each other; an inlet opening formed on the outer housing of vaporization assembly, an air inlet arranged on the vaporization assembly at an end where the vaporization assembly is connected with the control assembly, a vapor flow vent hole formed on outer wall of the joint between the e-cigarette liquid cup and the vaporizer, the vapor flow channel formed by the space between the inner housing of vaporization assembly and the outer wall of the e-cigarette liquid cup, the vapor flow outlet, and a channel inside the mouthpiece, together constitute a continuous vapor flow pathway; and the outer housing of vaporization assembly and the outer housing of control assembly are tightly connected in a sleeve type, in order to make sure that the bell-mouth structure and outer edge of the vapor flow outlet can be tightly pressed against each other and can be hermetically connected. the outer edge of the vapor flow outlet is hermetically connected with a bell-mouth structure, which is formed on the mouthpiece and is made of soft material, in a manner of being pressed against each other; an inlet opening formed on the outer housing of vaporization assembly, an air inlet arranged on the vaporization assembly at an end where the vaporization assembly is connected with the control assembly, a vapor flow vent hole formed on outer wall of the joint between the e-cigarette liquid cup and the vaporizer, the vapor flow channel formed by the space between the inner housing of vaporization assembly and the outer wall of the e-cigarette liquid cup, the vapor flow outlet, and a channel inside the mouthpiece, together constitute a continuous vapor flow pathway; and the outer housing of vaporization assembly and the outer housing of control assembly are tightly connected in a sleeve type, in order to make sure that the bell-mouth structure and outer edge of the vapor flow outlet can be tightly pressed against each other and can be hermetically connected.