The eccentric luminosity variations of quasars are still a mystery. Analytic results of this behavior ranged from multi-periodic behavior to a purely random process. Recently, we have used the non-linear time-series analysis techniques to analyze the optical light curve of 3C 273 and found that its eccentric behavior may be a low-dimensional chaos. This result induces us to seek some non-linear mechanism for the eccentric luminosity variation. In this paper, we propose a simple non-linear accretion disk model and find that under some circumstances, the chaos appears both in the disk and in the light curve. Then we compute the outburst energy ΔI, defined by the difference between the maximum luminosity and the minimum luminosity, and the mean luminosity 〈I〉 and find that when chaos appears, ΔI∼〈I〉 α ∼M 0.5α , where M is the mass of black hole and α≈1. These results are confirmed by and/or compatible with the observational data analysis.