1. Introduction
Quaternion matrices play important roles in quantum physics[1], Diagonalization theories are important parts in theories of quaternion matrices. Paper [2] studied a new proof of extended unitary diagonalizable of self-conjugate matrix in quaternion field. In paper [3], necessary and sufficient conditions of generalized diagonalization of quaternion matrices were studied and a method of generalized diagonalization was obtained. Paper [4] gave necessary and sufficient conditions for determining whether a quaternion matrix is a diagonalization matrix and proved Schur theorem over quaternion field. In this paper, we study some properties and the extended unitary diagonalization of skew self-conjugate matrix.