A thin type mechanical keyboard switch including a base and a keycap arranged on the base is provided. The base is provided with a first side accommodating groove, a conducting component. The base is further provided with a second side accommodating groove, a middle accommodating groove disposed between the first and the second side accommodating grooves, and a surrounding groove arranged around an upper end edge of the base. A balance rack is arranged in the surrounding groove, and the second side accommodating groove is provided with a torsional spring. The middle accommodating groove is provided with a blocking piece, a hanging piece, a tension spring and a guiding core. A through groove is formed between the first side accommodating groove and the middle accommodating groove. The through groove—is provided with a piston located between the guiding core and the conducting component.