Irregular casings filled with explosive charges are increasingly being developed for the designs of new warheads and explosive protection. In this work, we studied the fragment velocity of a semicircular D-shaped casing, which is a typical asymmetric casing. Static explosive experiments were conducted with D-shaped casings with different eccentric detonation coefficients (1/8, 3/8, 5/8, and 7/8) to determine their circumferential fragment velocity distributions. An empirical formula was then established to calculate the circumferential fragment velocity distribution for the D-shaped casing, and the calculation results of formula were found to agree well with experimental data. The D-shaped casing would have a uniform circumferential fragment velocity distribution when detonated at its central point, and the central point was determined by considering the empirical formula and the experimental data in combination. The results of the current work pave way for the innovative design of directional warhead and for further studying the dynamic response of asymmetric casing.