Abstract: Using the PCR amplification of the exon 6,14 and 15 of Si-1 gene.The deletion and mutation of Si-1 gene in the 116 malign tumors,1 carcinoid and 21 normal tissues were analyzed.Found 7 deletion and 8 intron mutation in malign tumors;none deletion and intron mutation in benign tumor;none deletion and 1 intron mutation in normal tissues were found.Especially the brain tumor has 57.1% deletion and 42.9% intron mutation,and the hepatocellular carcinoma also have 15.0% deletion and 26.7% intragenic mutation.All above of these,Si-1 gene has higher deletion and intron mutation of brain tumor and hepatocellular carcinoma,showing this gene may be as a marker gene of brain tumor and hepatocellular carcinoma.