Abstract: The location from where lightning initiate and the initial breakdown process of lightning are both important issues in research of lightning. In the summer of 2010, a series of 3D location data of lightning initial breakdown process are observed by two VHF broadband interferometers, which can provide the image of the development of lightning discharge with a time resolution of 5 μs and a space resolution better than 1 km. The initiation height distribution and 3D time-space characteristic of initial breakdown process in lightning are given by some statistical analysis on 80 intra-cloud lightning records and 61 negative cloud to ground lightning records. Results show that there are two obvious peak values, 5.0 km and 8.8 km above the ground, in the distribution of lightning initiation height. This two-peak feature can meet the picture described by the tripole gross charge structure of thunderstorms very well. The average velocities of 23 intra-cloud lightnings and 22 cloud-to-ground lightnings during the first 15 ms of initial breakdown process is calculated every 5 ms. The calculation indicates that the average velocities during the first 15 ms of initial breakdown process are in 10⁴-10⁵ order of magnitude both in intra-cloud flash and cloud to ground flash. Most intra-cloud flash and cloud to ground flash decelerated during the first 10-15 ms of the initial discharge. This result is a little different from a previous study in which all of the 24 intra-cloud flash records present a deceleration phase in the first 10-15 ms. It also demonstrates a possibility that runaway breakdown mechanism is not the only effective lightning initiation mechanism. Proportions of the intra-cloud flash which decelerated during the first 10 ms and 15 ms are both higher than those of cloud to ground flash in this observation. This may indicate that there is some difference between initiation processes of intra-cloud flash and cloud to ground flash. At last, it is found that the initial stage of intra-cloud lightning and cloud to ground lightning both have three possible development tendencies: Upward, downward and horizontal in vertical direction. The development direction of lighting initial stage is related to the environment electric field, and that can be used to give information about the direction of the electric field at the initiation location of lightning.