Background. The purpose of this study is to understand the oral mucosal immune status of cancer patients and to make clear whether antibacterial proteins such as salivary secretory immunoglobulin (SIgA) and lysozyme in saliva were influenced by patients' health status and certain medical treatment therapy. Materials and Methods. This study included 221 patients with malignant tumor receiving antineoplastic treatment and 171 age- and gender-matched healthy controls. Results. The results showed that patients suffering malignant tumor had lower level of SIgA and higher level of lysozyme than healthy subjects (P < 0.05). The SIgA level was significantly different among different cancer tumors, while the lysozyme level showed significant difference only between patients with digestive tract malignant tumor and hematopoietic system tumor. Pretreatment before transplantation for hematopoietic system tumor patients significantly affected the lysozyme level other than SIgA. SIgA level was affected by many factors such as age, therapy factors, and oral hygiene. Conclusion. Malignant tumor and the antineoplaston may weaken the patients' oral mucosal immunity, influence levels of some salivary proteins, and decrease the level of SIgA, resulting in aggregation of oral bacteria and failure of clearing them from the oral cavity.