The present application relates to cloud storage technology and especially relates to a cloud storage data access method, apparatus and system based on OTP. This method includes: generating and storing true random numbers of a predetermined length and a random seed of a predetermined length composed of the true random numbers via a preset method; acquiring data from the random seed for several times and cascading the data acquired each time into a true random data string of no shorter than the length of plaintext; based on the true random data string, generating a true random cryptographic key of no shorter than the length of the plaintext, encrypting the plaintext using this cryptographic key and transmitting ciphertext to a cloud storage data center. This application also provides a cloud storage data access apparatus and system based on OTP. The method, apparatus and system introduced by this invention can generate and store sufficient true random cryptographic key with relatively small physical space occupancy in comparison with that of plaintext, thereby enabling OTP to be applied into cloud storage data security protection.