To promote the research on curtain damping technology of explosion bubble and reveal the pulsation rule of underwater explosion bubble with low energy detonating cord(LEDC), an experimental research on the pulsation characteristics of underwater explosion bubble with single or two horizontal and vertical placed LEDC was carried out by a high-speed photography system. The pulsation characteristics of bubble under different placement of LEDC were obtained. The results show that the shape of the bubble pulsation at the first time is cylindrical when the single horizontal LEDC is exploded under water. The first period of the bubble pulsation is 11.5 ms, and the maximum diameter reaches to 6.9 cm. Under the conditions of two horizontal LEDC, the first period of the bubble pulsation is 14 ms and two bubbles begin to merge with each other and form a bubble curtain layer at 22 ms. The first period of the bubble pulsation of two horizontal LEDC is longer than that of one horizontal LEDC. Under the conditions of two vertical LEDC, the first period of the bubble pulsation is 27.5 ms. The first period of the bubble pulsation of two vertical LEDC is also longer than that of one vertical LEDC and a fully integrated bubble curtain is formed at 79.5 ms which is still visible at 323 ms. When the vertical placed LEDC are wrapped into a network, the bubble pulse duration is longer, and it was conducive to the formation of the explosion bubble curtain.