A single-longitudinal-mode Nd∶YLiF4 (Nd∶YLF) laser pumped by laser diode array, using a novel two-step Q-switching driver for the low-voltage KTiPO4 (KTP) Pockels cell was obtained. The amplitude and lasting time of the driver′s second step pulse is adjustable and the Nd∶YLF rod is end polished. Stable, low time jitter single longitudinal mode output was generated taking the advantages of prelase and etalon. The laser has produced pulse with width of 6.7 ns, energy of 1.156 mJ and a peak power of 0.17 MW. This laser holds the good single longitudinal mode probability of 100% and the stability of pulse energy of 3%. The time jitter between the Q-switching trigger and output pulse is less than 4 ns. The laser is easy to adjust and would have practical use in many fields with its simple peripheral electronic equipment and high reliability.