To investigate the effects of microplastics and phenanthrene on the growth, energy storage, stable isotope composition and stoichiometry of the discus fish (Symphysodon haraldi), here we set three microplastics concentrations (0, 100 and 1000 μgL-1) and two phenanthrene levels (0and 50 μgL-1), forming a total of six exposure combinations with three replicates per group for eight weeks. The results showed that: 1) Single exposure to microplastics or phenanthrene reduced the condition factor of the fish. The microplastics and phenanthrene in culture water had significant interaction with the hepatosomatic index of the juvenile discus fish, when the phenanthrene concentration was 50 μgL-1, 100 μgL-1 microplastics caused the hepatosomatic index of juveniles to increase. 2) The protein content of juvenile fish increased with the increase of phenanthrene concentrations. Microplastics and phenanthrene exposure had an interaction effect on the carbohydrate and crude fat contents of juvenile fish. When the phenanthrene concentration is 0 μgL-1, the increase in microplastics concentration would increased the crude fat content and reduced the carbohydrate content, but when the phenanthrene concentration is 50 μgL-1, the microplastics exposure would increased the crude fat and carbohydrate content. 3) The δ13C of juveniles increased with the increase of phenanthrene concentrations and decreased with the increase of microplastics concentrations. When co-exposed of microplastics and phenanthrene interacted with the δ15N value of juveniles, but the difference was not significant under different conditions. 4) Exposure to phenanthrene increased the N content and reduced the C/N of the fish. Co-exposed of both microplastics and phenanthrene had an interaction effect on the C and P content of juvenile fish: exposure to microplastics alone increased the C content and decreased the P content, when the concentration of microplastics is 50 μgL-1, phenanthrene exposure reduced P content. The results of this study suggest that exposure to microplastics and phenanthrene show no significant effect on the growth and survival of juvenile discus fish, but it might affect the energy storage status of the fish body, leading to changes in their stable isotope turnover and C, N and P stoichiometry characteristics and thus affecting the relative fatness and body quality of the discus fish. The results of this study can provide scientific basis for ecological risk assessment of microplastics and PAHs in fishery water environment.