Objective To explore the relationship between the levels of periodontal ligament associated protein 1 （PLAP-1） and absent in melanoma 2 （AIM-2） in gingival crevicular fluid， and the clinical stage， periodontal indicators， and prognosis of elderly patients with periodontitis. Methods A total of 104 elderly patients with periodontitis who presented at our hospital between February 2021 and February 2025 were selected as the research subjects. The patients were classified into the stage Ⅰ—Ⅱ group and the stage Ⅲ—Ⅳ group according to the clinical stage of periodontitis. Based on the results of the re-examination of periodontal pocket depth 6 months after periodontal basic treatment， the patients were divided into the good prognosis group and the poor prognosis group. The levels of PLAP-1 and AIM-2 in gingival crevicular fluid were measured by ELISA. The differences in the levels of PLAP-1 and AIM-2 among periodontitis patients at different clinical stages were analyzed. The correlation between the changes in periodontal indicators and the levels of PLAP-1 and AIM-2 was analyzed. The differences in the levels of PLAP-1 and AIM-2， as well as other data， among periodontitis patients with different prognostic conditions were analyzed. Additionally， logistic regression was employed to analyze the related factors influencing the prognosis of patients with periodontitis. The ROC curve was utilized to explore the predictive value of PLAP-1 and AIM-2 levels in gingival crevicular fluid for the prognosis of patients with periodontitis. The H-L test was used to assess the goodness of fit of the combined prediction scheme of the levels of PLAP-1 and AIM-2 in gingival crevicular fluid. Results The level of PLAP-1 in the stage Ⅲ—Ⅳ group was significantly lower than that in the stage Ⅰ—Ⅱ group， while the level of AIM-2 was significantly higher than that in the stage Ⅰ—Ⅱ group （P < 0.05）. The probing depth （PD） and attachment level （AL） of patients with periodontitis were negatively correlated with the level of PLAP-1 in gingival crevicular fluid and positively correlated with the level of AIM-2 （P < 0.05）. The level of PLAP-1 in gingival crevicular fluid in the poor prognosis group was significantly lower than that in the good prognosis group， and the level of AIM-2 was significantly higher than that in the good prognosis group （P < 0.05）. High levels of the deepest PD value and AIM-2， along with a low level of PLAP-1， were identified as risk factors for poor prognosis in elderly patients with periodontitis （P < 0.05）. The areas under the curve （AUC） for predicting the prognosis of elderly patients with periodontitis by the levels of PLAP-1 and AIM-2 in gingival crevicular fluid and their combination were 0.820， 0.832， and 0.895， respectively. The predictive efficiency of combining the two indicators was superior to that of a single indicator （Z_{PLAP-1-combined prediction} = 2.612， Z_{AIM-2-combined prediction} = 2.359， P = 0.009， 0.017）. The Hosmer-Lemeshow test for the goodness-of-fit of the combined test scheme showed χ² = 4.323 and P = 0.823， indicating good consistency. Conclusions The levels of PLAP-1 and AIM-2 in the gingival crevicular fluid of elderly patients with periodontitis are closely associated with their clinical staging， periodontal indicators， and prognosis. For elderly periodontitis patients who present with increased AIM-2 levels and decreased PLAP-1 levels in the gingival crevicular fluid， clinicians should closely monitor their oral condition.