Objective To compare the characteristics of attempted suicide in patients with schizophrenia， major depressive disorder， and bipolar disorder， to provide a scientific basis for developing suicide prevention frameworks for patients with different mental illnesses and to promote the further advancement of suicide prevention efforts. Methods This study was a cross-sectional study. From October 2022 to October 2024， 256 patients were enrolled from Beijing Huilongguan Hospital， Tianjin Anding Hospital， and the First Hospital of Shanxi Medical University. All patients met the diagnostic criteria for schizophrenia， major depressive disorder， or bipolar disorder as outlined in the Diagnostic and Statistical Manual of Mental Disorders， Fourth Edition（ DSM- Ⅳ） and reported a history of suicide attempts. Demographic characteristics， clinical features， and characteristics of the most recent suicide attempt were collected through patient interviews. Multiple Logistic regression analysis was conducted to compare clinical and suicide attempt characteristics across groups. Results This study included patients who reported suicide attempts， including 57 patients with schizophrenia， 140 patients with major depressive disorder and 59 patients with bipolar disorder. Compared with major depressive disorder group and bipolar disorder group， individuals with schizophrenia exhibited a higher proportion of "very few" suicidal ideation before their most recent attempted suicide［ 29.8%（17/57） vs. 7.9%（11/140） and 16.9%（10/59）］， with a statistically significant difference（ χ2=27.00， P＜ 0.01）. The proportion of individuals with attempted suicide in major depressive disorder group was higher than that in schizophrenia group［ 65.2%（90/140） vs. 45.6%（26/57）］， and the intensity of suicide intention was also higher than that in schizophrenia group［ 14.0（11.0，15.8） vs. 12.0（11.0，14.0）］， with statistically significant differences（ χ2/ H=6.39，7.10； both P ＜ 0.05）. The primary methods of suicide attempts across the three patient groups were low-lethality methods such as medication and cutting［ 66.7%（38/57）， 68.6%（96/140）， 67.8%（40/59）］， with no statistically significant differences（ χ2=0.37，P ＞ 0.05）. Multiple Logistic regression analysis revealed that compared with major depressive disorder group， patients with schizophrenia were significantly more likely to experience infrequent suicidal ideation before suicide attempts［ OR（95%CI）=15.47（1.25，191.52）］. Compared with major depressive disorder group or bipolar disorder group， schizophrenia group had lower levels of depressive disorder［ OR（95%CI）=0.77（0.69，0.86）， 0.82（0.73，0.92）］， higher levels of hallucinations［ OR （95%CI）=1.09（1.04，1.15）， 1.07（1.02，1.11）］， and higher levels of delusions［ OR（95%CI）=1.07（1.01，1.14）， 1.08（1.01，1.16）］. The level of social support in schizophrenia group was lower than that in bipolar disorder group［ OR（95%CI）=0.86（0.79，0.95）］. Conclusions Patients with schizophrenia exhibited significantly lower frequencies of suicidal ideation before attempting suicide compared to those with MDD and BD. Lowlethal methods such as medication and cutting were main methods of attempted suicide among all three groups. Therefore， suicide prevention efforts should strengthen the standardized management of medications and sharp objects to reduce accessibility risks. For patients with schizophrenia specifically， it is necessary to move beyond the suicide ideation-centered risk assessment model， and integrate their psychiatric symptoms to establish a more comprehensive evaluation and prevention system， which will facilitate precise suicide intervention for patients with different mental disorders.