Combining the spectra of could-to-ground lightning discharge processes obtained by a slit-less spectrograph with synchronous electric field information, the temperature, the conductivity, the current peak, electromagnetic power peak and the luminance of the discharge channel are calculated. The values are in a normal range reported by references. The correlation among cut-off time before a subsequent return stroke, the luminance and electromagnetic power peak of the channel is discussed. The change trends of the conductivity, the current peak and electromagnetic power peak are also investigated. The results show when cut-off time is long, neutralized charges will grow, the current will rise and electromagnetic power radiated from the channel will increase. When the conductivity and the peak of the electric field change increase simultaneously, the current in the channel will rise and electromagnetic power radiated from the channel will be greater. This work will provide some rferences for calculating optical and electromagnetic energy radiated by lightning discharge processes.