A variable attenuator, comprising at least one-stage attenuator circuit, the at least one-stage attenuator circuit comprising a signal input end (208 or 212), a signal output end (209 or 213), and a common grounded end (210 or 214), a first serial resistor (201 or 211) being disposed between said signal input end (208 or 212) and said signal output end (209 or 213) whereby forming a main signal circuit, and a first parallel resistor (202 or 217) being connected to said common grounded end (210 or 214); characterized in that a gap is disposed between said first parallel resistor (202 or 217) and said main signal circuit or is disposed between said first parallel resistor (202 or 217) and said common grounded end (210 or 214); the at least one-stage attenuator circuit further comprises a first conductive sheet (204 or 221) and a second conductive sheet (205a or 215); said first conductive sheet (204 or 221) and said second conductive sheet (205a or 215) are movable; said first conductive sheet (204 or 221) is adapted to be moved into a first position or a second position; said second conductive sheet (205a or 215) is adapted to be moved into a third position or a fourth position; when said first conductive sheet (204 or 221) is moved into the first position, said first conductive sheet (204 or 221) is disconnected from said signal input end (208 or 212) and said signal output end (209 or 213); and said second conductive sheet (205a or 215) is simultaneously moved into the third position and bridges the gap, whereby connecting said first parallel resistor (202 or 217) to said common grounded end (210 or 214); and when said first conductive sheet (204 or 221) is moved into the second position, said first conductive sheet (204 or 221) is connected to said signal input end (208 or 212) and said signal output end (209 or 213), whereby short circuiting said first serial resistor (201 or 211); and said second conductive sheet (205a or 215) is simultaneously moved into the fourth position and is disconnected from said first parallel resistor (202 or 217) and said common grounded end (210 or 214), whereby disconnecting said first parallel resistor (202 or 217) from said common grounded end (210 or 214). a gap is disposed between said first parallel resistor (202 or 217) and said main signal circuit or is disposed between said first parallel resistor (202 or 217) and said common grounded end (210 or 214); the at least one-stage attenuator circuit further comprises a first conductive sheet (204 or 221) and a second conductive sheet (205a or 215); said first conductive sheet (204 or 221) and said second conductive sheet (205a or 215) are movable; said first conductive sheet (204 or 221) is adapted to be moved into a first position or a second position; said second conductive sheet (205a or 215) is adapted to be moved into a third position or a fourth position; when said first conductive sheet (204 or 221) is moved into the first position, said first conductive sheet (204 or 221) is disconnected from said signal input end (208 or 212) and said signal output end (209 or 213); and said second conductive sheet (205a or 215) is simultaneously moved into the third position and bridges the gap, whereby connecting said first parallel resistor (202 or 217) to said common grounded end (210 or 214); and when said first conductive sheet (204 or 221) is moved into the second position, said first conductive sheet (204 or 221) is connected to said signal input end (208 or 212) and said signal output end (209 or 213), whereby short circuiting said first serial resistor (201 or 211); and said second conductive sheet (205a or 215) is simultaneously moved into the fourth position and is disconnected from said first parallel resistor (202 or 217) and said common grounded end (210 or 214), whereby disconnecting said first parallel resistor (202 or 217) from said common grounded end (210 or 214).