Abstract: Due to the continued strain on global fish oil resources, the utilization of alternative fats such as vegetable oil in aquaculture feed has gradually increased. However, there are differences in the types and concentrations of fatty acids between vegetable oil and fish oil. In order to reveal the effects of fatty acids with different chain lengths and degrees of unsaturation on the growth, lipid metabolism, and non-specific immunity of aquatic animals, juvenile turbot (Scophthalmus maximus L.) with an initial body weight of (8.00±0.20) g were selected as the experimental subjects in this study. Eight isonitrogenous and isolipidic compound diets with different chain lengths and unsaturated levels of fatty acids were set up: control group (CON), palmitic acid group (PA), stearic acid group (SA), oleic acid group (OA), linoleic acid group (LA), linolenic acid group (ALA), arachidonic acid group (ARA), and docosahexaenoic acid/eicosapentaenoic acid group (DHA/EPA). The experiment was conducted in a recirculating aquaculture system at 18℃ for 8 weeks. The results showed that with an increase in dietary fatty acid chain length and unsaturated degree, the weight gain rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) of juvenile turbot exhibited an increasing trend. Notably, the ARA group displayed the highest WGR and SGR, while the DHA/EPA group exhibited the highest PER. Dietary variations in fatty acids had no significant effects on the ash and water content of juvenile turbot (P>0.05). However, crude protein content increased with rising fatty acid chain length and unsaturation degree, whereas crude fat content decreased. Moreover, as fatty acid chain length and unsaturated degree increased, the plasma cholesterol (T-CHO) content of juvenile turbot gradually decreased, while the plasma triglyceride (TG) content was the highest in SA group and the lowest in DHA/EPA group. Plasma low density lipoprotein (LDL-C) content decreased with the increasing fatty acid chain length and unsaturation degree, whereas the high density lipoprotein (HDL-C) showed an opposite trend. Further analysis of lipid metabolism-related genes in turbot liver showed that dietary fatty acids could control lipid synthesis and decomposition by regulating the expression of lipid metabolism-related genes (FAS, PPARγ, SREBP1, PPARα, and ACOX1). The total antioxidant capacity (T-AOC) of liver in PA group was the lowest, and was significantly lower than that in other treatment groups (P<0.05). The liver superoxide dismutase (SOD) and catalase (CAT) contents were the highest in DHA/EPA group, while the liver malondialdehyde (MDA) content was the lowest. Furthermore, gene expressions of pro-inflammatory factors (IL-1β, IL-8, MyD88, NF-κB p65, TLR2, TLR8, TLR9, and TNF-α) in PA and SA groups were significantly increased, whereas the expression of anti-inflammatory factor (TGF-β) was significantly decreased. Conversely, in LA, ALA, ARA, and DHA/EPA groups, the trend was reversed. These results suggest that dietary supplementation of fatty acids with longer chain lengths and higher unsaturated degree can significantly affect the growth, lipid metabolism and non-specific immunity of juvenile turbot.