Small ubiquitin-like modifier 1 (SUMO1) and environmental factors have been shown to be associated with nonsyndromic cleft lip with or without cleft palate (NSCL/P) in several populations. This study aimed at confirming the contribution of SUMO1 gene and environmental factors to nonsyndromic orofacial clefts risk in western Han Chinese. Four single-nucleotide polymorphisms were investigated in 212 case trios in western China using conditional logistic regression models and the transmission disequilibrium test under a case-parent trio design. Strong evidence of linkage and linkage disequilibrium was found between these markers and the disease in both single-nucleotide polymorphism analysis (T allele at rs6761234 [p = 0.0005, odds ratio [OR] = 1.82, 95% confidence interval [CI]:1.30-2.57) and C allele at rs12470401 (p < 0.0001, OR = 2.82, 95% CI: 1.90-4.19)] and sliding window haplotype analysis (T-T-T for rs6761234-rs12470401-rs7599810 [p = 0.018], C-C-G for rs12470401-rs7599810-rs6435133 [0.0033], C-T-T-T for rs6761234-rs12470401-rs7599810-rs6435133 [p = 0.018] among others). Interactions between mothers' passive smoking during the first trimester and C/C genotype of rs12470401 showed statistical significance (OR(0) = 2.53 and OR(1) = 8.83). Risk factors identified in this study may provide a better understanding of the etiological role of SUMO1 gene in NSCL/P incidence.