Based on the full length of eight hydrogen phytoene synthase（PSY 1）from NCBI databases，
this study designed specific sgRNA according to the PAM（proto adjacent motif）site of the gene sequence，
and constructed CRISPR/Cas9 Level 1 and Level 2 vectors. Then the designed vector was transformed to
Agrobacterium，by the Level 2 vector were used to transform the tomato cotyledons. The knockout efficiency of
sgRNA in tomato genome was detected by PCR product sequencing. The results showed that 22 of the 36 transgenic
plants showed a different number of base deletion，increase or interchanges in the targeting area of PSY 1. The
gene knockout efficiency was 61% by initial estimates. The technique of CRISPR/Cas9 mediated gene knockout was
established in this study. This technique could stably generate gene knockout in tomato.