Objective To investigate the clinical diagnostic value of plasma serine protease inhibitor Ka-zal-type 4(SPINK4)expression in colorectal adenocarcinoma(CRC)and progressive adenoma(AA).Methods A total of 62 patients with CRC(CRC group)and 15 patients with AA(AA group)diagnosed by colonoscopy and pathological examination in this hospital from June 2020 to December 2021 were selected,and 22 healthy people undergoing physical examination during the same period were selected as the HC group.The expression of SPINK4 in plasma was detected by ELISA,and the expression of CEA in plasma was detected by electrochemiluminescence,and the correlation was analyzed.The diagnostic efficiency was analyzed by re-ceiver operating characteristic(ROC)curve,and the expression of p53 in CRC tissues was detected by immu-nohistochemistry.Results The expression of plasma SPINK4 in the CRC group and AA group was lower than that in the HC group(Z=3.72,-0.41,P＜0.05),and the expression of CEA in the CRC group was higher than that in the HC group(Z=-3.63,P＜0.05).The area under the curve(AUC),accuracy,sensi-tivity and specificity of SPINK4 combined with CEA in the diagnosis of CRC and AA were higher than those of SPINK4 and CEA alone.The positive rate of mutant type p53 in SPINK4 low expression group and CEA high ex-pression group was significantly increased in CRC patients(72.55％,75.00％,P＜0.05).Conclusion The expression of plasma SPINK4 is decreased in CRC and AA,and the combined detection of SPINK4 and CEA has a good di-agnostic efficiency in CRC and AA.