The invention discloses a slice fixing device for preventing a slice from falling. The slice fixing device is characterized by comprising a platform and a slice clamp, wherein a slice groove for accommodating the slice is formed in the top of the platform; the slice clamp is connected with the platform and used for fixing the slice in the slice groove; a first surface contact is formed by one side of the slice and the slice clamp; a second surface contact is formed by the other side of the slice and the slice groove; and angles between the contact surface of the first surface contact and the midperpendicular of the slice and between the contact surface of the second surface contact and the midperpendicular of the slice respectively are 30-50 DEG and 35-50 DEG. According to the slice fixing device for preventing the slice from falling, provided by the invention, the plane contact of the slice and the slice groove in the prior art is changed into 45-DEG inclined plane contact; a 45-DEG inclined acting force is applied to the slice through the slice groove contact surface; and the falling problem caused by the upwarp of the slice is effectively avoided through the decomposed acting force in the vertical direction.