1. A data modulation method, comprising the step of using a processor to perform steps of: receiving a first data sequence; arraying the first data sequence to a first matrix with n×n dimensions; providing a sparse matrix with n×n dimensions; multiplying the first matrix by the sparse matrix to generate a second matrix with n×n dimensions; executing a modulating and mapping procedure for generating a third matrix with (n+1)×n or n×(n+1) dimensions, wherein the third matrix is composed of a modulation part and an extra part; and storing the third matrix; wherein the sparse matrix is a binary matrix, each row in the sparse matrix has an odd number of elements, all rows in the sparse matrix have a same even number of bit 1 , all columns in the sparse matrix have a same even number of bit 1 , and the sparse matrix has an inverse matrix.