This paper mainly analyses and discusses the application and significance of the visual negative afterimage on the colour design of medical product based on the visual negative afterimage theory. The design for the colour of medical product based on the visual negative afterimage theory focuses more human orientation in aspect of the visual effect design. The paper also points out that the trend of future design is to organically combine the art, the therapy features and the humanity.The complementary colour equilibrium of the visual negative afterimage will play a more and more important role in the colour design of the medical product. In the modern medical environment, the colour of the medical product has a decisive effect on the information exchange between people and the space environment. Although the visual negative afterimage is common in our daily life, the colour is not taken into consideration in the colour design of the medical product, which will result in negative effects. The colour is a strong and extremely attractive expression tool. Therefore, when the colour is designed for the medical product, it should be applied reasonably. The application of colour must be based on the special function requirements and the use of different people, so as to show its special function and requirements, which not only avoids the negative influence caused by the visual negative afterimage, but also creates a more humanistic atmosphere for the medical environment.