In order to control digitally the print-through, the print-through standard of offset printing was studied in this article. For 4 given paper samples, the paper properties including paper opacity and K&N ink absorbency were tested, and then print-through value expressed with ΔD and ΔEab* was measured under 9 sets of printing condition. The results showed that lower printing press and higher printing speed were helpful to reduce the print-through. And under the same printing conditions, the print-through value of cyan ink print was slightly larger than that of magenta ink print. In addition, the print-through values of offset paper samples were a bit larger than that of newsprint samples. In particular, no matter what kind of conditions were, the print-through value expressed with ΔD and ΔEab* were lower than 0.04 and 4NBS when the PTR value was larger than 72%. The standard of print-through was firstly given, which was very helpful to choose paper during the offset printing.