The exact/approximate non-orthogonal general joint block diagonalization (nogjbd) problem of a given real matrix set A = {A i } m i=1 is to find a nonsingular matrix W ∈ R n×n (diagonalizer) such that W T A i W for i = 1, 2, . . . , m are all exactly/approximately block diagonal matrices with the same diagonal block structure and with as many diagonal blocks as possible. In this paper, we show that a solution to the exact/approximate nogjbd problem can be obtained by finding the exact/approximate solutions to the system of linear equations A i Z = Z T A i for i = 1, . . . , m, followed by a block diagonalization of Z via similarity transformation. A necessary and sufficient condition for the equivalence of the solutions to the exact nogjbd problem is established. Two numerical methods are proposed to solve the nogjbd problem, and numerical examples are presented to show the merits of the proposed methods.Key words. joint block diagonalization, tensor decomposition, independent component analysis AMS subject classifications. 15A21,15A69, 65F30.1. Introduction. The joint block diagonalization problem, also called the simultaneous block diagonalization problem, is a particular case of the block term decomposition (BTD) of a third order tensor [10,11,14,26]. Such problem has found many applications in independent subspace analysis (e.g., [4,13,30,31]) and semidefinite programming (e.g., [18,8,2,9]). To specify the problem, we name the problem by nine capital letters wwxyyzzzz. The first two letters, ww, indicate the type of the matrices in the matrix set, sy/he for real symmetric/complex Hermitian matrices, ge for general matrices. The second letter, x, indicates that the problem is solved in the exact sense or the approximate sense, e for the former and a for the latter. The next two letters, yy, indicate the type of the diagonalizer, no/nu for non-orthogonal/non-unitary matrix, o/u for orthogonal/unitary matrix(often left as blank). The last four letters, zzzz, indicate the computation performed, jd for joint diagonalization, jbd for joint block diagonalization, gjbd for general joint block diagonalization. Next, we first give some definitions, then formulate the wweyyjbd problem and the wweyygjbd problem mathematically.Definition 1.1. We call τ n = (n 1 , . . . , n t ) a partition of positive integer n if n 1 , n 2 , . . . , n t are all positive integers and the sum of them is n, i.e., t i=1 n i = n. The integer t is called the cardinality of the partition τ n , denoted by card(τ n ). The set of all partitions of n is denoted by T n .Definition 1.2. Given a partition τ n = (n 1 , . . . , n t ), for any matrix A of order n, define its block diagonal part and off-block-diagonal part associated with τ n as Bdiag τn (A) = diag(A 11 , . . . , A tt ), OffBdiag τn (A) = A − Bdiag τn (A), respectively, where A ii is of order n i for i = 1, . . . , t. A matrix A is referred to as a τ n -block diagonal matrix if OffBdiag τn (A) = 0.