A new Li2CO3-ammonia-ballmilling system was developed to synthesize the spinel Li4Ti5O12 (LTO) with perfect crystal structure. Different from other method for preparing LTO, two Li sources of Li2CO3 and LiOH are dynamic in-situ generation in this mechanical chemistry method, which leads to a hydrate precursor with the pre-arranged 4-cooperated Li+ and 6-cooperated Li+. The capacity of obtained LTO reaches 175.1 mAh g(-1) at current rate of 0.5C and keeps nearly 100% capacities even after 300 cycles. A hydrate transforming process in site was proposed to explain the good performance. And more, its capacities at high rates could be enhanced obviously by coating an N doped C layer.