Triggering lightning experiment with rocket-wire technique was conducted in Gansu, northwestern China. Ten cases of triggered lightning were obtained in three summers from 1989 to 1991. They were all with positive electric field at ground (positive charge overhead) under the influence of dominant lower positive charge of Gansu thundercloud. Triggered lightnings were weak discharges initiated by upward moving negative leaders followed by continuous current processes. No dart leader--return stroke processes were observed. The discharge lasted about several tens of miliseconds with a peak current of only a few hundred amperes. Simple physical models are used to evaluate the velocity of leader propagation, magnitudes, and altitudes of the charge transferred by triggered lightnings. Results are consistent with the features of lower positive charge of Gansu thunderstorms. ¿ American Geophysical Union 1994