Abstract: The 15 TW laser pulses were used to systematically study laser wakefield acceleration based on ionization injection. In the experiments, the influence of plasma density, interaction position, laser pulse duration and laser energy on the charge, divergence, pointing stability, energy and generation probability of electron beams was studied. When laser pulses with about 400 mJ and 25 fs are focused on the nozzle’s front and plasma density is about 9×10¹⁸ cm^-3, the generation probability of electron beams is as high as 100%. And, stable electron beams with horizontal (vertical) divergence of (6.5±0.5) mrad ((5.3±0.3) mrad), horizontal (vertical) pointing stability of ±1.2 mrad (±0.7 mrad), peak energy of (135±8) MeV and charge of (13.5± 2.0) pC (>50 MeV) are obtained, paving a solid foundation for its application.