AIM: To investigate the frequency of idiopathic phacodonesis (IP) in senile cataract subjects and the short-term clinical outcomes following cataract surgery. METHODS：This institutional case-control study included 1301 consecutive low-income cataract subjects from June to November 2009. Anterior segment were carefully evaluated with dilated pupil under slit-lamp. IP were screened and graded by a criteria set by the authors. Risk factors, surgical outcomes, and operative complications were analyzed. RESULTS：A total of 42 subjects (3.2%) with IP were diagnosed and classified as grade 1 (36 subjects), grade 2 (5 subjects) and grade 3 (1 subject). Harder lenses and intumescent cataracts were observed in the IP group than the control group (P<0.05). Logistics regression test also indicated the main risk factor was the hardness of the lens. The incidence of zonular dialysis during surgery was 23.8% (10 eyes), which was significantly higher than the controls (0.7%,P<0.001). Visual outcomes of the two groups were not statistically or clinically significant. CONCLUSION: Hard nucleus and intumescent cataract are related to IP in senile cataract subjects in Qinghai, China. With more care being taken, grade 1 and some of the grade 2 IP subjects achieved similar surgical outcomes as compared to controls.