In this paper, we develop an analytical model to evaluate the performance of optical burst switching (OBS) node with optical-level buffers for retransmission of blocked bursts. First, currently used burst blocking models and modelling of optical buffers at OBS nodes are shown to be inappropriate as a blocking model for retransmission in OBS nodes. Thus, we propose a new blocking model for the burst transmission mechanism with retransmission technique in an optical-level buffered OBS node. From the numerical analysis, we show the performance enhancement by applying optical buffers for retransmission of blocked bursts in terms of burst blocking probability and link utilization.