Objective To evaluate the accuracy of the biometry using immersion B scan and partial coherence interferometry (Lenstar LS900) for the axial length (AL) of silicone oil-filled eyes respectively. Methods Thirty-five silicone oil-filled eyes (38 patients) were included in the study. All of these eyes underwent silicone oil removal, cataract extraction and intraocular lenses implantation. The AL of all the silicone oil-filled eyes was measured with A/B-scan ultrasound and Lenstar LS900 before operation and with Lenstar LS900 after operation. The measured distance was compared respectively. The method of immersion B-scan guided with respective sonic velocity. AL was the sum of corneal thickness, anterior chamber depth, lens thickness, the apparent length of oil bubble (velocity values 996 m/s), the depth of the water layer beneath the oil bubble. Results Thirty-one eyes were measured with Lenstar LS900 before silicone oil removal, and the mean AL was (24.12±1.70) mm, 7 eyes failed to get the results before the operation; 36 eyes were measured with Lenstar LS900 after silicone oil removal, and the mean AL was (24.45±1.89) mm. All eyes were measured with B-scan before silicone oil removal, and the mean AL was (24.87±2.52) mm. The difference (31 eyes) of AL measurement before silicone oil removal by two methods was (−0.00±0.09) mm; the difference (31 eyes) between pre- and post-surgical AL measurement with Lenstar LS900 was (0.02±0.07) mm; the difference (36 eyes) between pre-surgical AL measured with B-scan and post-surgical AL measured with Lenstar LS900 was (−0.02±0.11) mm. All the differences were not statistically significant (t=−0.205, 1.752, −1.280; P＞0.05). The consistency of the results measured by two methods was well in Bland-Ahamn analysis. Conclusions Measurement results of AL between immersion B-scan guided with respective sonic velocity and Lenstar LS900 are high repeatability on silicone oil-filled eyes. The AL of silicone oil-filled eyes can be measured reliably by immersion B-scan guided with respective sonic velocity.