The present invention provides an isolated recombinant oncolytic adenovirus, a pharmaceutical composition, and an application of the isolated recombinant oncolytic adenovirus in a medication for treatment of a tumor and/or cancer. The recombinant oncolytic adenovirus is a replication-selective oncolytic adenovirus, and a coding sequence of exogenous shRNA capable of inhibiting PDL1 expression in tumor cells is integrated in a genome of the recombinant oncolytic adenovirus. The replication capability of the virus in normal primary cells is much lower than the replication capability of the virus in tumor cells; moreover, the expressed shPDL1 can significantly reduce the high PDL1 protein expression level in the tumor cells; thus, the oncolytic killing effect of the oncolytic virus and the anti-tumor immunostimulatory effect of immune cells can produce a synergistic effect.