Abstract: Objective To study the effects of different ratios of S/M/P fatty acid on serum lipid in rats on the premise that the current energy ratio of fat is 35%.Methods Seventy-two male rats were divided into 6 groups randomly.The experiment dietary S/M/P ratios were set at 1:117:112,1:1:1,2:1:1,1:2:1 and 1:1:2.The serum lipids were measured 12 weeks after the rats fed with different experimental diets.Results The groups with ratio of S/M/P of 1:1:1 had lower serum T G level than the group with ratio of 1:117:112,2:1:1 and 1:2:1(P<0105),and the ratio 1:1:2 even lower than the former(P<0.05).The group with ratio of 2:1:1 had higher serum TC and LDL level than the other groups.The groups with ratio of S/M/P 1:1:1 had higher serum HDL level(P<0.05),and the grpup of 1:1:2 even higher(P<0.05),and at the end of 12 weeks,the serum levels of HDL were 0.59±0.12(mmol/L)and 0.61±0.15(mmol/L).Conclusion The group with S/M/P ratio of 1:1:1 and 1:1:2 may be considered to be beneficial to serum lipid level,and it suggests that the high PUFA diet affect more favorably TG and HDL levels.