In this paper, a new 2-D phased array signal processing method for structural health monitoring (SHM) of thin orthotropic composite laminates is presented. The new method is developed by applying experimental wavenumber and wavefront curves to the same algorithm structure of the original 2-D phased array signal processing. The wavenumber and wavefront curves are experimentally determined for thin unidirectional and cross-ply laminates. Piezoceramic-based 2-D spiral phased array is used as a sensor array, and multiple piezoceramic elements are used as actuators in the experiments. Damage detection of the composite laminates is investigated with the spiral array and the new signal processing method, using the guided Lamb wave (GLW) technique.