Disclosed are a data sending method based on visible light communication and a sending end device. The method comprises: acquiring a target brightness value; extracting, from a plurality of code words of an output portion of an mBnB code, 2m permissible code words corresponding to the target brightness value, wherein m and n are both positive integers, and n is greater than m; determining that a mapping relationship between 2m code words of an input portion of the mBnB code and the 2m permissible code words of the mBnB code is an encoding mapping rule of the mBnB code; according to the encoding mapping rule of the mBnB code, encoding data to be sent to obtain first encoded data; and sending first brightness value information and the first encoded data to a receiving end device, wherein the first brightness value information is used for reflecting the encoding mapping rule of the mBnB code. The embodiments of the present invention can improve the data transmission efficiency of a VLC system.