Several　relationship　models　for　thermodynamic　functions　of　actinide　and　lanthanide　compounds　are　built.　The　descriptors　such　as　the　difference　of　atomic　radii　between　metal　atoms　and　nonmetal　atoms　and　the　molecular　mass　are　used　in　quantitative　structure-activity/property　relationships.　The　relative　errors　for　entropy　and　heat　capacity　are　less　than　20%　in　the　majority　of　gaseous　compounds.　Similar　results　are　obtained　from　solid　compounds.