This paper presents some basic properties and applications of Clifford algebra,which is a unifi-cation and generalization of complex numbers,quaternions and vector algebra,which accurately and com-pletely describes the intrinsic properties of space-time.Clifford algebra provides a unified,standard,ele-gant language and tool for many mathematical and physical theories.Hypercomplex number systems have the potential to complete a new large synthesis of modern sciences and it is worthy to be popularized in teaching and scientific research.