The invention belongs to the technical field of oil and gas field exploration and development and particularly relates to an online detecting system for fracturing fluid performances. The online detecting system comprises a liquid inlet in a collecting end (2) of a suction tube of a sand mixing truck, wherein the liquid inlet is connected to a straight-through part (3) with an inductive probe connector; the other connector of the straight-through part (3) is connected to one end of a low-pressure pipeline (4); the other end of the low-pressure pipeline (4) is connected to a suction end (6) of the sand mixing truck or an exhaust end (7) of a liquid storage tank; the inductive probe connector is connected to a viscosity induction probe (9), an acidity and alkalinity inductive probe (10) and a density inductive probe (11), each inductive probe is electrically connected to a signal acquirer (5); the signal acquirer (5) is in wireless connection to a remote receiving device (1) on a meter truck (8). The online detecting system for fracturing fluid performances can be used for improving the fracturing fluid viscosity measuring precision, also can be used for measuring the fracturing fluid pH value and the density value, has the functions of acquiring and transmitting measured data, and is convenient for the construction staff to grasp the fracturing fluid performances.