Objective To investigate the relationship of frail status with readmission and death in senile patients with primary osteoporosis. Methods A prospective cohort study was conducted to include 227 osteoporosis patients (≥65 years old) admitted to the General Department of Fuxing Hospital from January 2017 to December 2019. According to the results of Clinical Frailty Scale (CFS-09) after admission, they were divided into frailty group (CFS ≥5) and non-frailty group (CFS <5). General data, such as gender, age, medical history and oral medication were collected, and comprehensive geriatric assessments, including Mini-Mental State Examination and Mini-Nutritional Assessment-Short Form were performed for their cognitive function and nutritional risk. After discharge, all patients were followed up for 1-3 (1.8±0.7) years, and their readmission and death were recorded. SPSS statistics 23.0 was used for statistical analysis. Data comparison between 2 groups was performed using student′s t test, Wilcoxon test or Chi-square test depending on data types. Cox regression analysis was used to investigate the relationship of frailty with readmission as well as death. Results The subjected patients were at a mean age of 67-100 (85.1±5.0) years, with a frailty prevalence of 53.3% (121 cases). The frailty group had older age (P<0.001), higher Charlson comorbidity index (CCI) (P<0.001), more types of oral medications (P=0.004), larger number and types of potentially inappropriate medication (PIM) (P=0.004,0.001), and larger proportions of nutritional risk (P<0.001), cognitive dysfunction (P<0.001) and impaired activities daily living (P<0.001) when compared with the non-frailty weak group. Cox regression analysis showed that after adjusting for age, comorbidity and PIM, frail state (CFS≥5) had no significant effects on death and re-hospitalization. When the patients were further assigned into moderate or above frailty subgroup (CFS≥6) and mild or non-frailty group (CFS<6), moderate or above frailty state (CFS≥6) significantly increased the risk of all-cause death (HR=3.260,95%CI 1.626-6.538, P=0.001) and readmission (HR=1.727,95%CI 1.213-2.458, P=0.002) after adjustment for age, comorbidity and PIM. Conclusion Moderate or above frailty as defined by CFS-09 (CFS≥6) increases the risk of death and readmission in elderly patients with primary osteoporosis. Clinicians should pay attention to the frailty assessment of osteoporosis patients and take intervention measures as early as possible to reduce the risk of death and readmission.