An experiment to determine the laminar burning velocity of premixed liquefied petroleum gas was conducted in a constant volume chamber with a centrally lit pilot flame at various beginning pressures. (LPG) / Ammonia / air flames was carried out. 100, 200, 300 KPa. Furthermore, the studied equivalency ratios ranged from 0.8, 1, and 1.3, and the explored ammonia mixes were 0 to 30% by volume. Laminar burning velocity, flame speed, and Markstine length experimental data. High-speed Schlieren imaging, an ignition control system, a mixing chamber, and data collection were employed. The findings of the experiments also demonstrated the effect of beginning pressure on laminar burning velocity, demonstrating that as initial pressure rises, laminar burning velocity decreases. At a pressure of 100 kPa, an equivalence ratio of 0.8, and a concentration of ammonia 30%, it became a value of 24.56 cm/s. and the same conditions and an initial pressure of 200 kPa, the value of the laminar burning velocity reached 19.64 cm/sec The results showed that the gradual increase of ammonia gas reduces the combustion speed, at an initial pressure of 100 kPa , equivalence ratio of 1 and ammonia gas concentration 10%, the combustion velocity became 39.32 cm/sec, and at the same conditions and an initial pressure of 100 kPa and ammonia concentration 30%, the combustion velocity reached 34.945 cm/sec.