Holters may accommodate the demand of daily health monitoring of hearts. [14][15][16] But current ECG monitoring systems either contain small numbers of leads that are used as consumer electronics for diagnosing limited numbers of symptoms [17][18][19][20] or contains multiple rigid leads that are prone to the influence of motions and are unable to conduct dynamic measurement. [21,22] Flexible electronic systems have demonstrated their capabilities in adapting skin contour and skin motion, minimizing the issues of motion artifacts and mechanical mismatches between conventional rigid electronic materials and soft skin. They have been demonstrated as varieties of wearable sensing patches to record physical parameters such as temperature, [23,24] humidity, [25][26][27] blood pressure, [28][29][30] and strain [31,32] as well as chemicals such as ions, [33,34] glucose, [35,36] and blood oxygen. [37,38] Flexible ECG systems have also been explored in the context of stretchable electrodes, [39,40] novel conductive electrode materials, [40][41][42][43] capacitive sensing, [44,45] and flexible hybrid electronics. [46][47][48] However, the majority of these ECG systems are based on single lead detection with a small sensing area, lacking the capability to comprehensively probe the hearts from different angles and the compatibility with clinical standards that are built on 12-lead ECG. [49,50] Flexible 12-lead ECG systems may offer precise and comprehensive detection results that abide by the clinical requirements with excellent tolerance to body motion and skin contour. However, such systems have seldomly been reported due to the complexity in constructing flexible systems that cover large surface areas while maintaining high stability in motion and skin deformation. As a result, a flexible 12-lead system in integrating with skin and potential influence factors to the performance of this system has rarely been studied.Here, we developed a flexible 12-lead ECG system that can simultaneously conduct electrocardiogram sensing and threeaxis acceleration monitoring. The system that contains a flexible sensor formed by modularized components and a flexible wireless measurement circuit. The sensing components are screen-printed and assembled to cover almost the entire chest area with adjustable dimensions to adapt to different body shapes. The design of individual components in the sensor Dynamic multilead monitoring of cardiovascular health conditions is challenging due to the complexity of constructing a flexible system that covers large surface areas and synchronizes measurement results from different leads. A flexible 12-lead electrocardiography system that can simultaneously conduct electrocardiogram sensing and 3-axis acceleration monitoring is developed. The system is fabricated through a modularized printing process, resulting in individual modules that can be assembled reversibly through magnetic connectors. Different levels of stretchability and adjustable length of interconnect can accommodate different body statures a...