Male killer whales and female killer whales are different in size, but this is limited to killer whales of the same age. If they are different in age, they may be the same in size. Usually, if they are killer whales of the same age, the males are slightly larger than the females. Adult male killer whales can grow up to 8 meters long, and the longest can even reach 9.75 meters. Male and female killer whales can only grow up to 7 meters and 8.5 meters long.

Since female killer whales and male killer whales are different in sex, their reproductive organs must be different. Generally, after the killer whale matures sexually, it can judge its western sex through its reproductive organs. If it has one reproductive fissure and two mammary fissure, then it must be a female killer whale. If it has two reproductive fissure and no mammary fissure, it means it is a male killer whale.

Female killer whales and male killer whales have great differences in dorsal fin. The first is their dorsal fin height. In adulthood, the dorsal fin height of male killer whales is very high, while that of female killer whales is much lower. Then there is the shape of their dorsal fins. The shape of the dorsal fins of male killer whales is generally upright and basically triangular; Female killer whales' dorsal fins are generally curved and shaped like sickles.