Abstract: This paper studies the coUisionless magnetic reconnection in the presence of different guide fields using two-and-a-half dimensional full particle simulation. The results show that, a strong guide field with Bz0 〉 0.5B0 will not only strongly alter the motion of electrons but also change the structure of electric field and velocity field around the reconnection region, thus affect the reconnection rate and electron accelerating process. General Ohm＇s law for two-fluid MHD model is employed to explain the characteristics of these electric field structures. And by tracing beams of electrons near the diffusion region, it is found that in the 2D model, electric field component perpendicular to the simulation plane and located at the center of diffusion region plays the major role in the electron acceleration, while the other two components contribute very little, no matter the guild field is strong or not.