With the rapid development of digital information techniques, the use of DNA media for information storage is considered as the future direction of data storage. Existing DNA storage schemes simply map compressed binary multimedia data into DNA base data, which has the disadvantages of data loss, low logical storage density and high cost of synthesis. This paper presents an end-to-end high density DNA encoding algorithm(referred to as HD-code, where HD stands for high density). The novelty and contributions of this work contain three parts. First, by taking full advantage of the statistical characteristics of the original multimedia data and considering the biological constraints on the DNA bases, the proposed scheme achieves higher logical storage density and improves the flexibility and consistency in data storage. Second, by performing data conversion, the proposed scheme can effectively encode extreme images with large proportion of single color. Third, the proposed method can reconstruct high quality images and reduce synthesis costs by yielding better rate-PSNR(Peak Signal to Noise Ratio).