A novel three-dimensional chaotic attractor derived from Colpitts equation is proposed. This chaotic system is developed by using a square term to substitute for exponent term in normal Colpitts equation. Lya-punov exponent, Poincar-mapping, phase portrait and power spectrum are given to verify that the attractors are chaotic. Based on bifurcation diagram and Lyapunov exponent spectrum, some basic dynamical characteristics of the new system are investigated briefly and the physics process from fixed point, periodic to chaotic behaviors are disclosed simultaneously. Finally, the PSpice simulation for circuit implementation is given out which shows good agreement with the numerical simulation.