The present invention discloses a determination and location method of a 10kV distribution network one-phase default fault. The method comprises the following steps of: the step 1, regulating a starting voltage of an electroscope to make the starting voltage of the electroscope higher than a voltage of the phase-default phase at a high-voltage side of a transformer; performing call measurement orfield measurement of three-phase phase voltage values of a low-voltage side of the transformer of a distribution line by a remote information collection system, and when a phase voltage value is normal and an absolute value of the difference between the other two voltage values and the voltage value of a normal phase is smaller than 3V, determining that the fault type is one-phase default of the transformer, wherein the transformer is located at the load side of the phase-default point; and the step 2, employing the electroscope regulated in the step 1 to detect each-phase voltage at the high-voltage side of the transformer in the step 1, when an acousto-optic indication device of the electroscope is inactive when one phase is only measured, determining that the phase is a default phase, reducing the fault range into the phase of the transformer, and indicating the default phase point to the power source side of a high-voltage access point of the transformer. The determination and location method of a 10kV distribution network one-phase default fault can determine the fault position with no need for seeing a fault phenomenon.