AbstractThe long-term orbital period changes of detached chromospheric active binaries were surveyed. 17 of such systems are found to be undergoing secular period decreasing with the rates (dP/dt) of −3.05 × 10⁻⁹ to −3.77 × 10⁻⁵ days per year. The longer the orbital period, the more rapidly the period decreases. Following Stepien (1995), the period decreasing rate due to the angular momentum loss (AML) caused by magnetic wind is computed for each system. A comparison shows that the observed dP/dt's are obviously higher than that of the theoretical predictions by 1-3 orders of magnitude. It suggests that the magnetic wind is not likely the determinant mechanism driving the AML in close binaries.