A data transmission method, comprising: obtaining to-be-transmitted K bits, wherein the to-be-transmitted K bits have been channel coded; mapping the K bits to F resource units, wherein each bit in the K bits is mapped to at least two resource units in the F resource units, and K and F are integers greater than 1, wherein the mapping the K bits to F resource units comprises: dividing the K bits into V bit sequences; and mapping the V bit sequences to the F resource units, wherein each bit sequence in the V bit sequences is mapped to at least two resource units in the F resource units, and V is an integer that is greater than 1 and less than or equal to K; and mapping the bits mapped to the F resource units to a modulation symbol for transmission; wherein a bit a in the K bits is mapped to f1 resource units in the F resource units, and a bit b in the K bits is mapped to f2 resource units in the F resource units, wherein the bit a mapped to the f1 resource units is separately mapped to f1 bit carry positions on the modulation symbol, and the bit b mapped to the f2 resource units is separately mapped to f2 bit carry positions on the modulation symbol; a sum of transmission reliability indicator values corresponding to the f1 bit carry positions is f1 +, and a sum of transmission reliability indicator values corresponding to the f2 bit carry positions is f2 +, wherein an absolute value of a difference between f1 + and f2 + is less than or equal to a threshold; and the bit a and the bit b are any two bits in the K bits; a larger transmission reliability indicator value indicates higher transmission reliability of a corresponding bit carry position, or a smaller transmission reliability indicator value indicates higher transmission reliability of a corresponding bit carry position. obtaining to-be-transmitted K bits, wherein the to-be-transmitted K bits have been channel coded; mapping the K bits to F resource units, wherein each bit in the K bits is mapped to at least two resource units in the F resource units, and K and F are integers greater than 1, wherein the mapping the K bits to F resource units comprises: dividing the K bits into V bit sequences; and mapping the V bit sequences to the F resource units, wherein each bit sequence in the V bit sequences is mapped to at least two resource units in the F resource units, and V is an integer that is greater than 1 and less than or equal to K; and dividing the K bits into V bit sequences; and mapping the V bit sequences to the F resource units, wherein each bit sequence in the V bit sequences is mapped to at least two resource units in the F resource units, and V is an integer that is greater than 1 and less than or equal to K; and mapping the bits mapped to the F resource units to a modulation symbol for transmission; wherein a bit a in the K bits is mapped to f1 resource units in the F resource units, and a bit b in the K bits is mapped to f2 resource units in the F resource units, wherein the bit a mapped to the f1 resource units is separately mapped to f1 bit carry positions on the modulation symbol, and the bit b mapped to the f2 resource units is separately mapped to f2 bit carry positions on the modulation symbol; a sum of transmission reliability indicator values corresponding to the f1 bit carry positions is f1 +, and a sum of transmission reliability indicator values corresponding to the f2 bit carry positions is f2 +, wherein an absolute value of a difference between f1 + and f2 + is less than or equal to a threshold; and the bit a and the bit b are any two bits in the K bits; a larger transmission reliability indicator value indicates higher transmission reliability of a corresponding bit carry position, or a smaller transmission reliability indicator value indicates higher transmission reliability of a corresponding bit carry position.