Aiming at the damage monitoring problem of typical marine composite material structures, a new method for monitoring the damage location of composite materials is proposed, and the relationship between static loading load and damage expansion coefficient is established. For damage location monitoring, based on signal spectrum and correlation coefficient, a Bayesian-based damage probability imaging method is proposed, and a multi frequency weighted damage imaging update method is proposed. For damage expansion research, three damage expansion coefficients are constructed according to the time-domain signal characteristics of ultrasonic guided waves and hyperbolic tangent function, and the damage expansion coefficients under different static loading loads are obtained. Experimental results show that the Bayesian-based damage probability imaging method can accurately locate the damage location; the variation law of damage expansion coefficient with increasing load provides technical support for the damage expansion of typical composite material structures.