The shot coke formation in delayed coking unit in Petrochina Liaoyang petrochemical company is introduced when processed the mixture of Russian and Venezuela vacuum Residue. The production of shot coke has been avoided by optimizing operating parameters and adjusting mixing ratio of feedstock. Production practice has proved that changing operating conditions has no obvious effect on generation of shot coke. Improvement on properties and composition of feedstock is close related with formation of shot coke.