<p>Chemical indicators in sweat are critical for monitoring health status, and wearable sweat-sensing technologies are attracting substantial attention for their role in the non-invasive and continuous monitoring of molecular-level insights. However, existing sweat-sensing technologies often require a substantial volume of sweat to maintain stable signal output, severely limiting their real-life applications. Here, we introduced a core/shell structured electrochemical sensing fiber consisting of a carbon nanotube (CNT) fiber core and a super hydrophilic cotton fiber shell, achieving an impressive sweat capture efficiency of 90% at a low-sweat rate of 0.4 μL cm⁻²&#xa0;min⁻¹. Specifically, upon contact with sweat, the super hydrophilic cotton fiber in the outer shell of the fiber captures in 0.2&#xa0;s and rapidly transmits it to the sensing region in the inner core, enabling stable electrochemical sensing. Integrated into a smart T-shirt, the wearable sweat-sensing system accurately monitors multiple chemical aspects (e.g., Na⁺, K⁺, and pH) of sweat in real-time during moderate exercise, jogging, and mild activities such as walking.</p>