An oncolytic adenovirus vector and its potential application in cancer treatment and vaccination. The inventive vector (named Ad-TD-hIL12) is derived from the human adenovirus group C type 5, more particularly including deletion of three adenovirus genes E1A-CR2, E1B19K and E3gp-19K, and a fused cDNA sequence of p35 and p40 subunit of human IL12 placed under the control of the E3gp-19K promoter. The invention also includes a method to construct the triple gene-deleted vector (Ad-TD). The Ad-TD-hIL12 and Ad-TD-shIL12 (with a short p40 sequence of human IL 12) vectors can be used as targeted, genetically engineered agents for treatment of various solid tumors, via not only intratumoral injection, and also in intraperitoneal injection, without causing significant side effects, showing a superior antitumor efficacy and safety.