Abstract: The requirement on the novel solder joint materials is one of the critical topic studied in electronics packaging. In this paper, nickel-coated carbon nanotubes added SAC305 were prepared by mechanical mixing method. The mode I fracture test was carried out based on the fabricated DCB double cantilever specimen . Based on the test, the load-displacement curve of the specimen was obtained. The beam method theory based on compliance (CBBM) was used to extract the mode I fracture toughness of the fabricated solder. The results show that the mode I fracture toughness of the solder increases first and then decreases with the increase of the additive content. The mode I fracture toughness of SAC305 solder without additive content was about 0.53 N/mm, and the solder with 0.05wt% content of additive shows the highest mode I fracture toughness is about 1.14 N/mm. Compared with SAC305 solder without nickel-coated carbon nanotubes, the mode I fracture toughness of the solder was increased by 1.15 times, which shows better crack propagation resistance.