In this paper, a novel highly sensitive fluorescent aptasensor was constructed and used to detect ochratoxin A based on gold nanoparticles/aptamer/amino-functioned carbon quantum dots by using self-assembly. Gold nanoparticles/aptamer/amino-functioned carbon quantum dots were prepared as following. First, thiol-modified aptamer was attached to the surface of the gold nanoparticles in pH 3.0 tartaric acid-HCl buffer to form gold nanoparticles/aptamer by assembling. Second, amino- functioned carbon quantum dots were added to the gold nanoparticles/aptamer dispersion to form gold nanoparticles/aptamer/amino-functioned carbon quantum dots under electrostatic interactions in phosphate buffer solution (pH 7.0), by removing the excessive amino-functioned carbon quantum dots with centrifugation. The fluorescence of the amino-functioned carbon quantum dots was efficiently quenched by the gold nanoparticles, which are excellent quencher for fluorescence sensing as they have very high molar extinction coefficients and broad energy bandwidth. The fluorescent intensity of the quenched system was background fluorescence (F0). When ochratoxin A was addition to the fluorescence quenched system, the specific reaction between aptamer in the nanocompostes and ochratoxin A took place, simultaneously, amino-functioned carbon quantum dots were released, and a turn on amino-functioned carbon quantum dots fluorescence signal (F) was detected. The emission intensity increase (F-F0) could be used for the quantification of the amount of ochratoxin A in samples. The influence facts on the sensor performance were investigated including the molar ratio of gold nanoparticles and Apt, pH and incubation time. The optimum conditions were gold nanoparticles∶aptamer=1∶190 in molar ratio, pH 7.0 and incubation time was 6 minutes. Under the optimum conditions, a linear fluorescence signal response to ochratoxin A concentration was over a wide ochratoxin A concentration range of 0.005～1.00 ng·mL-1. The linear regression equation is: F-F0=6.499+211.6 ｃ(ng·mL-1), linear correlation coefficient is: r=0.995 5 with a diction limit of 3 pg·mL-1 according 3σ/k (σ: relative standard deviations, k: slope of the working curve). The recovery was between 93.3%～108.9% in real samples, and the relative standard deviation was less than 5%. The proposed method was employed to detect ochratoxin A in beer samples, the results showed that ochratoxin A was found in 6 of 13 beer samples, with a positive rate of 46.15%. The concentration of ochratoxin A was in the range of 0.008～0.63 ng·mL-1. The fluorescent apasensor method used to detect ochratoxin A has the advantages of highly sensitive, highly specific, without interference of common mycotoxins, simple, very fast, convenient for popularization and application.