The crystal structure of mathiasite, a new mineral from Sbandong provin- ce, has been determined, and the crystal chemical formula is written as(K, Ca) (Ti, Cr, Fe, Mg, Zr)21O38. The mineral belongs to trigonal system having space group of R3, with its cell parameters being a=10.3722A，c=20.7161A，aR= 9.1403A and a=69.137°. 1554 independent diffraction data were collected on RASA-5RP auto-four- circle single crystal diffractometer; coordinates, temperature factors and site occupancies for all atoms were obtained and refined; atomic distances and ang- les were calculated. The final deviation factor R is 0.047. Mathiasite occurs in lcimberlite and must have formed under high tempera- ture and pressure. Through the determination of its structure, the coordination about such atoms as Ti, Cr, Mg and K, especially. the coordination about Zr atom in the complex oxide dominated by Ti, has been revealed. This research contributes to the mineralogy and crystal c乡emistry of acces- sory metallic minerals in kimberlite.