Embodiments of the present invention provide a data transmission method and system, a base station, and a user equipment (UE). The method includes: obtaining, by a base station, a second number of physical resource blocks (PRBs) according to a first number of PRBs, where the second number of PRBs is smaller than the first number of PRBs, and the first number of PRBs is exactly divisible by the second number of PRBs; sending, by the base station, indication information to a UE, where the indication information is used to indicate the second number of PRBs or an encoded bit repetition multiple, and the encoded bit repetition multiple is equal to the first number of PRBs divided by the second number of PRBs; and obtaining, by the UE, the encoded bit repetition multiple according to the indication information, and performing data transmission according to the encoded bit repetition multiple.