Predicting wake morphology during debris flow when passing a cylindrical obstacle is vital for disaster assessment, early warning, evacuation planning, engineering design, and ecologic conservation. It can provide a scientific foundation for pertinent decision-making processes, diminishing the risks and impacts of debris flow disasters. This study extracts the morphological characteristics of debris flow cylindrical flow traces through the steady-state motion of debris flow observed in a flume during cyclical tests. It introduces a theoretical prediction formula and compares it to empirical data. The results indicated that the morphology of debris flow cylindrical flow traces can be described as a wall-jet-like bow wave (a bow wave formed by an upward wall jet on the obstacle upstream face). The primary upstream inflow is predominantly discharged through the wall and lateral jets. Formulas for three crucial parameters that determine the morphology of the traces are derived by combining the aerodynamics theory and extant literature. The predicted outcomes strongly align with the experimental data, underscoring their high predictive precision.