A testing system for float liquid level transmitter includes a computation unit, an operation interface, a storage unit and a display unit. The computation unit computes basic data associated with the float liquid level transmitter to obtain corresponding standard values and the display unit displays the standard values. After a float liquid level transmitter performs measurement, the computation unit fetches displayed values measured by the float liquid level transmitter and obtain an error range by comparing the displayed values with the standard values; the computation unit analyzes the error range to provide analyzed data and determines whether the float liquid level transmitter is qualified based on the error range.