To meet the requirements for intelligent monitoring of depth and temperature in marine environments, a multimodal sensing biomimetic jellyfish robot system was designed and implemented. A shape memory alloy (SMA)-actuated jellyfish robot was adopted as the biomimetic carrier, and flexible pressure and temperature sensors were integrated to establish a multimodal sensing basis. A hardware acquisition circuit composed of a main controller module, a power supply module, and a multi-channel signal acquisition module was developed. Serial communication, ADC data conversion, pressure-signal filtering, and dynamic baseline correction were used for signal processing, and real-time visual monitoring of multimodal information was achieved. It was demonstrated by the experimental results that water-depth variation during robot ascent could be effectively characterized by the pressure modality, and periodic disturbances caused by propulsion rhythms during horizontal swimming could also be reflected. External water-temperature variations under both stationary and swimming conditions are stably characterized by the temperature modality, and no significant change in response trend is caused by robot motion. The designed system integrates bionic form, flexible drive and multi-modal perception in a unified manner. It demonstrates great potential for application in aspects such as intelligent monitoring of the water environment in the ocean, multi-modal perception of flexible underwater robots, and subsequent intelligent decision-making research.