Abstract: Upper union bounds of turbo codes for maximal ratio combining (MRC) diversity systems are presented in this paper. The simplified expression of error integral function is used to derive the precise expressions of pairwise error probability for MRC receivers wherein the probabilities of slow fading multichannel come from different distribution families. The numerical analysis and simulations performed over Rayleigh channel demonstrate that the theoretical analysis conforms to the simulations. It is concluded that the derived expressions can be generally used for the performance estimation of MRC multichannel receivers with different fading statistics.