The invention discloses a biomimetic mechanical jellyfish that is driven by shape memory alloy wires, relates to a biomimetic mechanical jellyfish and aims at solving the problems that the existing biomimetic mechanical jellyfishes only simulate jellyfish actions, do not cover devices such as a drive device and the like, and have complex structure and the biomimetic effect that is totally different with the action principle of real jellyfishes. The biomimetic mechanical jellyfish has following structure: an action unit (10) consists of the shape memory alloy wires (12), an elastic body (13), a coating skin (15) and a substrate (16), the substrate (16) and the shape memory alloy wires (12) are fixedly arranged on the elastic body (13), the action unit (10) is coated inside an umbrella-likesoft layer (11), the coating skin (15) covers outside the shape memory alloy wires (12), the substrate (16) and a sealing cover (3) are fixedly connected with a supporting body (2), a power source (7), a control device (5), a communication device (6) and a sinking and floating control device (9) are fixedly arranged on the supporting body (2), and the power source (7) provides electricity respectively to the control device (5), the communication device (6) and the shape memory alloy wires (12). The biomimetic mechanical jellyfish has simple structure, lightness, low production cost, large action range and good biomimetic effect.