Most eukaryotic protein-coding genes are split into exons and introns, and introns need to be spliced for the production of mature mRNA by pre-mRNA splicing. Pre-mRNA splicing is very important for eukaryotic gene expression, because it is not only a key step in producing mature mRNA, but can also affect transcription and translation. The purpose of this study is to investigate the relationship between gene expression and splicing efficiency since the relationship has not been studied systematically from a bioinformatic approach. In this thesis research, we focus on the question of how gene expression would constrain the evolution of three principal splicing signals: the donor splice site, the acceptor splice site, and the branchpoint sequence (BPS).