Abstract: An intracardiac ultrasound probe and a catheter system. An innovative design of flexible circuit boards and multi-core coaxial cables are used. The flexible circuit boards are extended in length or width, and the multi-core coaxial cables are configured to connect to the flexible circuit boards, so that a thickness and width of the flexible circuit boards soldered with the multi-core coaxial cables are within an allowable range of an inner diameter of a bendable ultrasound catheter. The multi-core coaxial cables reduce the coupling crosstalk between the array element signals, improve the electromagnetic shielding effect between wires, avoid the phenomena of reduced image detail and contrast resolution, thus facilitate a better image quality compared to prior art.