Exon 5～8 of p53 gene in 10 cases of non small cell lung cancer(NSCLC)tissues and normal lung tissues were examined by nonisotopic polymerase chain reaction-single strain conformation polymorphism(PCR-SS-CP).It showed that there was point mutation in 4 cases of cancer tissues. The mutant points were 1 in exon 5～6,1 in exon 7,2 in exon 8 respectively. Otherwise,no point mutation was observed in normal lung tissues. Mutant p53 gene determined by PCR-SSCP was sequenced and found that codon ACA 280 instead of AGA 280,that is, cysteine instead of serine.