Ancient Chinese paintings and calligraphy boast a long history, but many diseases occur in very old collections. Consequently, traditional restoration techniques for paintings and calligraphy have been developing. Based on experience, observing and analyzing diseases is an important precondition to developing a restoration plan. But the shedding of pigment is a secondary disease occurring during restoration. It is often overlooked during planning, which may then cause the destruction of painting, loss of color and dimming, and even the loss of parts of content. The disease is extremely harmful to paintings, so it is important to research the secondary shedding of pigment during restoration and optimize related restoration techniques. Based on practical experience, we carefully researched the secondary shedding of pigment during restoration, analyzed its cause from the perspective of materials and techniques, and proposed criteria for its prevention. This work could provide reference for the research on diseases of ancient paintings and calligraphy as well as the optimization of restoration techniques.