Memristor with memory function is the fourth fundamental two-terminal circuit element, besides resistor, capacitor and inductor. In this paper, a smooth flux-controlled memristor is described by a monotone-increasing nonlinearity curve in the -q plane, and it has an italic type 8 like voltage current relation curve that looks like a pinched hysteresis loop characteristics. By replacing Chua's diode with an active memristor consisting of a smooth flux-controlled memristor and a negative conductance, a memristor based chaotic oscillation is derived from Chua's circuit. Furthermore, the equivalent circuit implementation form for the active memristor is designed by utilizing conventional components such as operational amplifiers and multipliers. The results from theoretical analysis, numerical simulations and circuit simulations are completely identical with each other, and demonstrate that the dynamical behaviors of the memristor chaotic circuit are dependent on the memristor initial state, showing different orbits such as chaotic oscillation, periodic oscillation and stable sink under different initial states.