Objective To improve the vigilance and awareness of malignancy presenting as dermatosis and reduce misdiagnosis. Methods Two cases of gastric cancer presenting as dermatomyositis and erythroderma respectively in the last two years were retrospectively analyzed and the relevant literatures were reviewed. Results The two patients were admitted to hospital due to skin diseases， diagnosis of gastric cancer through endoscopy， and proved to be gastric cancer associated with dermatosis by pathological examination after surgical resection. Conclusions Paraneoplastic dermatoses can be seen as an early manifestation of the internal malignancy. The patients with paraneoplastic dermatoses should be excluded visceral tumors by the means of biomarkers， endoscopy， PET/CT， and so on.