In response to the current status of helicopter sling flight research both domestically and internationally, this paper proposes a helicopter sling flight control law design method based on H∞ theory. Taking the UH-60A Black Hawk helicopter and CONNEX container as examples, a single-point sling model is used to connect the helicopter with the suspended load. The dynamics equations of both the helicopter and suspended load are modified using the sling model to complete nonlinear dynamic modeling. Wind disturbance inputs are incorporated into the model, and small perturbation theory is applied to linearize the model, leading to the design of an H∞ controller. Numerical simulations were conducted to test the control performance of the H∞ controller under sensor noise, showing excellent velocity control. Additionally, robustness tests with changes in the mass of the suspended load demonstrate that the H∞ control law maintains effective control under varying load conditions, proving its excellent control characteristics and robustness in helicopter sling flight.