Sub-micron Li1.4Al0.4Ti1.6(PO4)3 (LATP) ceramic powder is synthesized by a co-precipitation method which can be applied for mass production. A pure Nasicon phase is confirmed by X-ray diffraction analysis and the primary particle size of the product is 200–500nm. The sinterability of LATP is investigated and the relative density of 97% reached at a sintering temperature as low as 900°C for 6h. The bulk lithium ionic conductivity of the sintered pellet is 2.19×10−3 Scm−1, and a total conductivity of 1.83×10−4 Scm−1 is obtained.