Objective: To compare the consistency of OA-2000 with IOLMaster 500 and A-scan for biologicalmeasurements. The purpose of this study was to evaluate the measurements of OA-2000 in preoperative examinations of cataract patients. Methods: In this case series study, a total of 152 patients (152 eyes) diagnosed with age-related cataract were selected at the Affiliated Hospital of Nei Mongol Medical University from May to June 2018. All the patients were examined in turn by OA-2000, IOLMaster 500 and A-scan. Measurements by these three instruments were compared for axial length (AL), Ks/Kf, anterior chamber depth (ACD), white-to-white (W-W), lens thickness (LT) and intraocular lens (IOL) dioptor. The results were analyzed by one-way analysis of variance, Pearson correlation and Bland-Altman. Results: ①The detection rates of AL and ACD with OA-2000, IOLMaster 500, and A-scan were 97.3%, 78.2%, 100%, and 99.3%, 97.3%, 100%, respectively. The detection rates of Ks/Kf with OA-2000 and IOLMaster 500 were 99.3% and 98.6%. The detection rates of W-W with OA-2000 and IOLMaster 500 were 97.3% and 94.7%. Among them, 17 eyes had high myopia, posterior scleral grape swelling and an axial length≥26 mm. The detection rates of AL with OA-2000, IOLMaster 500 and A-scan were 88% (15/17), 65% (11/17), and 100% (17/17). ②There was a significant difference in AL and ACD between the three instruments (F=12.63, P=0.02; F=10.57, P=0.01). The AL, ACD parameters measured by OA-2000 and IOLMaster 500 were not significantly different. There were significant differences in AL and ACD between A-scan and the other two instruments (P<0.001). There were no significant differences in Ks/Kf, IOL or W-W parameters among the three instruments. ③The average difference in AL measurements between OA-2000 and IOLmaster 500 was 0.03 mm, between OA-2000 and A-scan was 0.13 mm. The average difference between the three instruments for AL measurements with an axial length≥26 mm: OA-2000 and IOLmaster 500 was 0.06 mm; OA-2000 and A-scan was 0.43 mm. ④A Pearson correlation analysis showed that there was a high correlation between the measured results of OA-2000 and IOLMaster 500 (r=0.78, P=0.02). ⑤The consistency of AL results using Bland-Altamn analysis showed that there was good consistency in the range of 95% consistency. Conclusion: There was a high consistency in ocular biological measurements between the three instruments in cataract eyes. However, the detection rate of OA-2000 in AL was significantly higher than that of IOLMaster 500, and the accuracy of the OA-2000 measurement was obviously higher in the AL measurement in high myopia with posterior staphyloma.