A speaker box includes a housing with an accommodating space and a housing wall; a propping wall extending from the housing wall toward the accommodating space; and a speaker unit located between the housing wall and the propping wall for dividing the accommodating space into a front cavity and a back cavity. The speaker unit includes a diaphragm located in the front cavity for forming a front sound cavity cooperatively with the housing, a sound guiding channel communicating the front sound cavity with outside, and a through hole penetrating the propping wall and communicating the sound guiding channel with the back cavity. The speaker box further includes an elastic cover plate covering the through hole completely for absorbing vibration energy at a specific frequency. The Young's modulus or strength of the elastic cover plate is smaller than that of the propping wall.