A flexible catheter-based in vivo detection device and system. The in vivo detection device comprises: a detection part (1), a primary circuit board (3), a detection circuit board (2), secondary circuit boards (4), a cable wire, and an outer catheter (7). A first side surface of the detection circuit board (2) is provided with a first conductive material (21). The detection part (1) is connected to the first side surface of the detection circuit board (2) and a wiring terminal of the detection part (1) is soldered to the first conductive material (21). A second side surface of the detection circuit board (2) is provided with a second conductive material (22). The second side surface of the detection circuit board (2) is connected to a second edge of the primary circuit board (3). The second conductive material (22) is vertically soldered to a conductive portion on the surface of the primary circuit board (3). The first conductive material (21) is electrically connected to the second conductive material (22). Each secondary circuit board (4) is connected to a first edge. A channel for at least part of an instrument catheter (6) to pass through is formed between the two secondary circuit boards (4). The in vivo detection device and system can effectively improve the strength and reliability of soldering in the case that a packaging size is limited.L'invention concerne un dispositif et un système de détection in vivo faisant appel à un cathéter souple. Ce dispositif de détection in vivo comprend : une partie détection (1), une carte à circuit imprimé primaire (3), une carte à circuit de détection (2), des cartes à circuit imprimé secondaires (4), un fil de câble et un cathéter externe (7). Une première surface latérale de la carte à circuit imprimé de détection (2) est pourvue d'un premier matériau conducteur (21). La partie détection (1) est connectée à la première surface latérale de la carte à circuit imprimé de détection (2) et une borne de câblage de la partie dét
