The slewing and luffing coupling motion of tower cranes can easily induce structural vibrations in the crane mast and swing angles of the payload, potentially leading to operational faults. To investigate these vibration patterns, an elastic crane model was developed under combined slewing and luffing dynamic motions, incorporating Lagrange dynamics, air resistance, and beam deflection. The model was analyzed across phases from acceleration to constant speed and then to deceleration. The effectiveness of this nonlinear coupled motion model was validated using a designed experimental platform. The study examined the effects of varying accelerations and initial swing angles. The results indicate that luffing acceleration influences structural vibration, while slewing acceleration has a significant impact on it. Additionally, initial angles greater than or equal to 0.2 rad greatly affect structural vibration. When the slewing acceleration exceeds 0.04 m/s², the frequency of mast vibration increases. Understanding the structural vibration law during coupled motion is crucial for enhancing the design of dynamic systems.