The present invention relates to a method of constructing a low density Parity Check code, a method of decoding the same and a transmission system using the same. The method comprises steps of: constructing a low density Parity Check matrix of the low density Parity Check code by using a fixed pattern; blocking data sent from an information source (101), encoding the data by directly or indirectly using the constructed low density Parity Check matrix to obtain codewords of the low density Parity Check code; and outputting the codewords of the low density Parity Check code. The low density Parity Check code can be encoded by using the Parity Check matrix or a generation matrix. According to the proposed constructing method, a Parity Check matrix of a low density Parity Check code having excellent performance, a method of constructing the low density Parity Check code and a complexity-reduced decoding method can be obtained.