The invention discloses an improved Hele-Shaw box and a two-phase fluid density difference convective mixing experimental system formed by the improved Hele-Shaw box. The experimental system comprises a CCD camera, the improved vertical type Hele-Shaw box, and an area light source. By adopting the improved vertical type Hele-Shaw box, a lower layer fluid space sealed by a rotary switch is filled with small density fluid, and an upper layer fluid space is filled with large density fluid. The CCD camera, the improved vertical type Hele-Shaw box, and the area light source are disposed in a camera bellows. The rotary switch is used to rotate a rotating shaft arc surface to a gap between two layers of parallel light-transmitting materials to seal lower layer fluid. The large density fluid is disposed in the upper part of the Hele-Shaw box in a filled manner. The switch is opened, and the upper layer fluid and the lower layer fluid are contacted with each other, and a convective mixing experiment caused by a fluid-fluid two-phase fluid density difference is started, and at the same time, the CCD camera starts to shoot the images of the two-phase liquid convective mixing process. The experimental system has advantages of simple structure, convenient operation, accurate timing, and applicability in subsequent researching of interphase boundary changing, fingering generation development time, fingering numbers and other characteristic parameters during convective mixing process.