1. Look at the abdomen: the male crab's abdomen is triangular and pointed; the female crab's abdomen is round or oval and more rounded.

2. Look at the legs: male crabs have dense hairs on all eight legs, while female crabs only have dense hairs on the front two legs.

3. Look at the gonads: you can also distinguish them by the gonads in their bodies. The paragonads in the bodies of male crabs are crab paste, which is a translucent gelatinous substance.