Trans fatty acids (TFA) have been considered as an independent risk factor of coronary heart disease, sudden death and insulin-resistance, and different TFA isomers may have different effects on the progression of cardiovascular diseases such as atherosclerosis. The aim of the study was to investigate the effects of two major TFA, elaidic acid and linolelaidic acid which have the same number of carbons but a different number and configuration of trans bonds, on the proliferation of human umbilical vein smooth muscle cells (HUVSMC). Methyl thiazolyl tetrazolium and flow cytometry assays showed that the cell proliferation rose to 115.37 ± 0.39 and 117.5 ± 0.57 % and the cell number in the S phase of the cell cycle reached 27.7 ± 0.7 and 25.8 ± 2.8 % when treated with 50 μM elaidic acid and 20 μM linolelaidic acid, respectively. Quantitative real-time reverse transcriptase-polymerase chain reaction and Western blotting analyses showed that the two TFA increased the mRNA and protein expression levels of PCNA, CDK2 and Cyclin E in HUVSMC. Moreover, gas chromatography analysis showed that the total PUFA level of HUVSMC was lower after treatment with the two TFA, especially n-3 PUFA. These results suggested that linolelaidic acid exhibited a stronger proliferative effect on HUVSMC than elaidic acid, and regulation of CDK2 and Cyclin E may be important for the effect of the TFA on atherosclerosis.