Based on the principle of the volume holographic data storage, the technologies and its main systems of holographic data storage are reviewed. The principle, system structure and coding method of the collinear holographic data storage system are introduced and analyzed. In the absence of mature phase encoding principle, two kinds of phase encoding of phase-modulated collinear holographic data storage systems are analyzed and evaluated. These two phase encoding methods effectively complement the possible methods of phase encoding in holographic storage. The pairs-phase-encoding improves the code rate and reduces the error rate compared with traditional encoding. Moreover, a multilevel complex amplitude modulated collinear holographic storage system is introduced, which can efficiently reduce material consumption and increases storage capacity. Moreover, its system performance is evaluated. Consequently, more reasonable coding method, appropriate modulation and suppression of noise, are still urgent problems in the researching of holographic data storage technology.