Long-term observations show that blazar object S5 0716 +714 has complicated behavious on multiband. In this paper, the light curves in the radio, V-band and X-ray bands of four outbursts are studied by the chaos theory. We calculate their correlation dimensions and Lyapunov exponents and find that 1) these two values are in a range between a stochastic system and a pure chaotic system; 2) the phase locus of S5 0716 +714 is a chaotic system similar to the Rossler attractor. Various internal or external factors may produce noises, resulting in the fact that the correlation dimension and Lyapunov exponent may be higher than those of the Rossler attractor and the phase locus might be orderless. According to our analysis, we conclude that the light curves of S5 0714+716 show some chaotic features and the variability of this source may be a chaotic phenomenon.