Objective:To investigate the risk factors of lymph node metastasis for patients with colorectal cancer in T 3 and T 4, and to provide a reference for clinical diagnosis and treatment. Methods:The clinicopathological data of 1 112 patients with colorectal cancer in T 3 and T 4 who underwent radical resection of colorectal cancer in Xijing Digestive Disease Hospital from January 2008 to December 2017 were retrospectively analyzed. The correlation between lymph node metastasis status and the clinicopathological factors as well as tumor markers was analyzed. The related risk factors of lymph node metastasis were analyzed by using logistic multivariate regression analysis. Results:Univariate analysis showed that there was no statistically significant difference in the incidence of lymph node metastasis among colorectal cancer patients stratified by gender, age and tumor location (all P > 0.05). The different tumor diameter [<5 cm and ≥5 cm: 37.75% (211/559), 52.26% (289/553), χ2 = 23.666, P < 0.01], general type [infiltration, ulcer, parasol, bulge: 37.04% (20/54), 47.52% (432/909), 34.33% (23/67), 69.51% (57/82), χ2 = 13.787, P = 0.003], degree of differentiation [highly-differentiated, moderately-differentiated, poorly-differentiated: 34.11% (102/299), 49.00% (317/647), 48.80% (81/166), χ2 = 19.771, P < 0.01], mismatch repair deficiency (dMMR) [yes and no: 26.34% (64/243), 50.17% (436/869), χ2 = 43.996, P < 0.01], neurological invasion [yes and no: 48.17% (421/874), 33.20% (79/238), χ2 = 16.954, P < 0.01], vascular invasion [yes and no: 79.16% (338/427), 23.65% (162/685), χ2 = 327.493, P < 0.01] and preoperative carcino-embryonic antigen (CEA) [positive (≥5 mg/ml) and negative (<5 mg/ml): 52.87% (249/471), 39.16% (251/641), χ2 = 20.162, P < 0.01] and CA199 [positive (≥35 U/ml) and negative (<35 U/ml): 59.33% (124/209), 41.64% (376/903), χ2 = 21.465, P < 0.01] had statistically significant differences in the incidence of lymph node metastasis for above stratified patients. Logistic multivariate regression analysis showed that vascular invasion and preoperative CA199-positive were independent risk factors for lymph node metastasis in patients with colorectal cancer in T 3 and T 4 ( OR = 13.006, 95% CI 9.329-17.276, P < 0.01; OR = 2.194, 95% CI 1.513-3.181, P < 0.01), and dMMR-positive was a protective factor for lymph node metastasis ( OR = 0.279, 95% CI 0.190-0.411, P < 0.01). Conclusions:Vascular invasion is the main risk affecting factor for the lymph node metastasis of patients with colorectal cancer in T 3 and T 4. The detection of preoperative tumor marker CA199 can be used as an index to predict the lymph node metastasis of patients with colorectal cancer in T 3 and T 4. To a certain extent, it can provide a reference for the diagnosis and treatment of patients with colorectal cancer in T 3 and T 4.