The invention relates to a charging type portable low-sampling-voltage-drop microamp micro-current monitoring system based pm a low-sampling-voltage-drop and low-power-consumption design. An operational amplifier is a low-bias current low-noise precise chopper type amplifier using a microamp micro-current I/V conversion circuit as a core; and various anti-interference protection circuits are used. A single lithium battery is used for a storage and supply unit for power; USB type charging is selected by using a charging switch and system type charging is selected by a power selection switch; and the system power supply is provided by means of cooperation of a USB unit and the lithium battery to complete microamp micro-current monitoring. According to the invention, the provided system can be used as a portable measurement instrument and can be applied to an indoor occasion, an outdoor occasion or other occasions needing monitoring; the lithium battery is used for power supply on an indoor occasion or an outdoor occasion; and power supply also can be realized by means of USB. The monitoring instrument has a same size as a palm; the weight is light; the portability and monitoring precision are high; the prices is low; and the testing can be carried out conveniently; and a corresponding conversion voltage value can be tested as long as the to-be-measured micro current is connected according to a requirement.