Abstract: Both traditional and dual quaternion-based velocity update algorithms for strapdown inertial navigation system (SINS) are comparatively studied. The leading cause of difference in accuracy between the two algorithms is analyzed and determined in principle. By defining both truncation and approximate integral errors, the difference in accuracy can be not only described qualitatively but also computed quantitatively. The validity of theoretical analysis and derivation is verified through simulation testing. The significant superiority of the dual quaternion algorithm over the traditional one in accuracy is demonstrated through simulation results under highly-dynamic and large-maneuver conditions. Comparison results under both ideal and real dynamic conditions show that the dual quaternion algorithm is superior to the traditional one in overall performance.