A recombinant oncolytic virus, a synthetic DNA sequence and applications of the virus. The recombinant oncolytic virus includes a genome and an exogenous DNA sequence inserted in the genome. The exogenous DNA sequence adapts to express a basic peptide fragment, to increase the environmental pH in a host infected by the recombinant oncolytic virus. More than 60% of amino acids in the basic peptide fragment are basic amino acids. The recombinant oncolytic virus and the synthetic DNA sequence of the disclosure are used to prepare an anti-tumor drug.
