Rupture of the thin fibrous cap of the atherosclerotic plaque is the primary cause of acute coronary syndrome accounting for more than half of all cardiovascular deaths. Fibrous cap thickness (FCT) is seen as critical to plaque vulnerability. In this study, the intra-observer reproducibility of FCT and the correlation analysis between FCT and intravascular optical coherence tomography (IVOCT) images features were implemented to find the relationship between FCT of lipid-enrich plaques and images information by two observers. We performed IVOCT pullbacks in consecutive series on 20 patients and selected 102 images containing lipid-enrich plaques. Firstly, region of interests (ROIs) were extracted by an unsupervised fuzzy c means clustering (FCM) stage. Then, 32 features, which are associated with the structural and biochemical changes of tissue within the ROIs, were carried out using First order statistics (FOS), Gray level co-occurrence matrix (GLCM), Neighborhood gray tone difference matrix (NGTDM), Invariant moment (IM), Fractal dimension (FD) and Shape features (SF). Finally, the FCT in grayscale IVOCT images were manually measured by two independent observers. The intraclass correlation coefficient (ICC) was 0.80 for two different observers. The image features with ROI region and FCT showed a high correlation coefficient for both observers (r=0.88, p<0.001 and r= 0.91, p<0.001, respectively). The results suggest that the features of IVOCT images based FCT measurements may be useful to quantify the plaque cap thickness and vulnerability.