An improved gene sequence optimization method, the systematic optimization method, is described for boosting the recombinant expression of genes in bacteria, yeast, insect and mammalian cells. This general method takes into account of multiple, preferably most or all, of the parameters and factors affecting protein expression including codon usage, tRNA usage, GC-content, ribosome binding sequences, promoter, 5′-UTR, ORF and 3′-UTR sequences of the genes to improve and optimize the gene sequences to boost the protein expression of the genes in bacteria, yeast, insect and mammalian cells. In particular, the invention relates to a system and a method for sequence optimization for improved recombinant protein expression using a particle swarm optimization algorithm. The improved systematic optimization method can be incorporated into a software for more efficient optimization.