Multicarrier code-division multiple access (MC-CDMA) techniques are widely considered as promising techniques for future wireless multimedia communications, since they can efficiently combat multipath propagation. In higher data-rate wireless application scenarios, modified MC-CDMA systems, which include a serial-to parallel (S/P) converting operation, are more applicable; they are named as modified MC-CDMA systems with the mixing model of replicating and S/P converting. This paper focuses on the channel identification problem of these modified MC-CDMA systems in the uplink. Based on subspace decomposition, we derive a novel channel identification scheme for the modified MC-CDMA system with the mixing model of replicating and S/P converting. Computer simulations illustrate the validity and the performance of our proposed algorithm.