The charge flux of plasma, the delay time of laser ignition and the absorbability of laser by plasma were tested to study the effects of plasma and ablation on laser ignition processes of energetic materials. Tested energetic material is B/KNO3 (m(B)∶m(KNO3)=40∶60)+additional 5% phenolic resin, 20 mg, under 37.92 MPa pressure. Laser set is a Nd∶YAG laser with 680 μs pulsed width. The density of plasma rises with increase of laser energy, and the charge flux of plasma is larger than that of combustion flow. The delay time of ignition is shorted with the rise of the energy density of laser linearly, but when the energy density increases over a critical value, the delay time keeps constant. The plasma do not almost absorb incident laser beam in the testing conditions, but experimental results of the delay time of ignition show that the ablation of laser prevents laser energy from depositing in energetic materials.