The paper presents a novel robust control of one class of nonlinear single-input single-output (SISO) systems with distributed delay on state used the auxiliary loop method. The problem is solved by introducing an auxiliary loop and using two Khalil observers to compensate for a generalized disturbance signal containing information not only about the parametric uncertainty of the installation model, but also information about distributed delay and disturbances. The designed control law is investigated in MATLAB. To illustrate the obtained results, an example of a nonlinear system with a distributed time delay is given. It is shown that the proposed control law under conditions of parametric uncertainty ensures the achievement of the goal with a given accuracy.