An apparatus and method for receiving data in a mobile station for a mobile communication system using multi-user packet data are provided, in which a preamble power measurer measures preamble power of the multi-user packet data received from a base station and transmits the result value to a controller. The controller compares the measured power with a predetermined threshold, simultaneously decodes the multi-user packet data according to all transport formats if the measured power is lower than the threshold, and decodes the multi-user packet data according to a predetermined transport format if the measured power is higher than or equal to the threshold. A plurality of decoders decode the received multi-user packet data according to a control signal from the controller, wherein the number of the decoders depends upon the total number of transport formats for the multi-user packet data.