Abstract: Objective To investigate computational method of intraocular lens power and analyze the causes of errors after cataract surgery for patients with high myopia. Methods Ninety-six eyes in 96 patients with high myopia who underwent phacoemulsification surgery by the same surgeon from January 2013 to December 2015 in Chinese PLA General Hospital were enrolled in this study. The "long axis length (AL)" was defined as AL group with length of 26-30 mm (n=55), and the "extreme long AL" was defined as AL> 30 mm group (n=41). Different formula (Haigis formula and SRK-T formula) and different measurement methods (A-mode Ultrasound and Master IOL) were used to calculate the length of the eye and intraocular lens degree. The difference between target preoperative refractive diopter and achieved postoperative refractive diopter (3 months after surgery), which was called "error value", was calculated separately. Results The mean AL was 29.40 mm. There was statistically significant difference in the error value between AL group and AL > 30 mm group (Z=-2.28, P=0.023), and the error value increased with the increase of the AL (r=0.257, P=0.011). The calculated error value did not differ significantly by Haigis formula or SRK-T formula (P> 0.05), while the error value measured by A-mode Ultrasound was smaller than IOL Master (Z=-2.75, P=0.006). Conclusion Calculation errors often occur after cataract surgery for patients with high myopia, known as "hyperopia drift", and the main reason is scleral staphyloma. There is no difference in measurement accuracy between Haigis formula and SRK-T formula. In the case of extreme long AL, A-mode Ultrasound is more accurate than IOL Master.