In this paper,we investigate the construction of time-varying convolutional low-density paritycheck(LDPC)codes derived from block LDPC codes based on improved progressive edge growth(PEG)method.Diferent from the conventional PEG algorithm,the parity-check matrix is initialized by inserting certain patterns.More specifically,the submatrices along the main diagonal are fixed to be the identity matrix that ensures the fast encoding feature of the LDPC convolutional codes.Second,we insert a nonzero pattern into the secondary diagonal submatrices that ensures the encoding memory length of the time-varying LDPC convolutional codes as large as possible.With this semi-random structure,we have analyzed the code performance by evaluating the number of short cycles as well as the the bound of free distance.Simulation results show that the constructed LDPC convolutional codes perform well over additive white Gaussian noise(AWGN)channels. In this paper, we investigate the construction of time-varying convolutional low-density parity check (LDPC) codes derived from block LDPC codes based on improved progressive edge growth (PEG) method. Life of the conventional PEG algorithm, the parity-check matrix is initialized by inserting certain patterns. More specifically, the submatrices along the main diagonal are fixed to be the identity matrix that ensures the fast encoding feature of the LDPC convolutional codes. Second, we insert a nonzero pattern into the secondary diagonal submatrices that ensures the encoding memory length of the time-varying LDPC convolutional codes as large as possible. Here the semi-random structure, we have analyzed the code performance by evaluating the number of short cycles as well as the bound of free distance. Simulation results show that the constructed LDPC convolutional codes perform well over additive white Gaussian noise (AWGN) channels.