A convolutional code rate matching method and a communication apparatus are provided. A puncturing pattern of a second codeword at a second code rate is obtained based on a puncturing pattern of a first codeword at a first code rate. A second puncturing location set of the second codeword is a subset of a first puncturing location set of the first codeword. When a transmit device decreases a code rate from the first code rate to the second code rate, a redundant bit is sent at a location of a complementary set of the second puncturing location set relative to the first puncturing location set. Compared with the first puncturing location set, the second puncturing location set may obtain more incremental redundant bits, to decrease a channel encoding rate. This can improve decoding performance of a convolutional code.