An LDPC code encoding and modulation method and a communications apparatus are provided to resolve a problem of poor transmission performance and low transmission reliability that are caused in an existing modulation method. Under the method, an information bit sequence Sb can be obtained. The Sb can be encoded by using a LDPC matrix H to generate an encoded code sequence Sc. The Sc can be modulated to obtain a modulated symbol sequence SM. This modulation may include mapping bits in a least reliable code block in the Sc to non-least reliable bit locations for constellation modulation. SM can be sent to a receive end. In this way, reliability of all symbols in the SM is relatively high and uniform. A bit error rate can be effectively reduced, so that encoding performance is improved and more reliable transmission is implemented.