An apparatus and method are provided for transmitting a symbol group in a mobile communication system. The method includes generating a symbol group to which an orthogonal sequence is applied; mapping the generated symbol group to an Orthogonal Frequency Division Multiple (OFDM) symbol based on a symbol group index and a Physical HARQ Indicator Channel (PHICH) group index; and transmitting the mapped symbol group. The generated symbol group is mapped to the OFDM symbol in an alternating pattern in accordance with the symbol group index.