For studying transport of hot electrons in solid targets by transition radiation (TR), the image pattern of spatial distribution and spectrum of optical emission were measured at the normal direction from the rear side of targets employing optical charge coupled device (CCD) camera and optical multi-channel spectrometer apparatus (OMA) on the 100 TW femtosecond laser facility. The image pattern of spatial distribution presents a tray-shape and in the tray-shape there is a bright localized signal, which shows filament effect during hot electron transport. The spectrum of optical emission presents a sharp peaks in the wavelength near 800 nm, which is attributed to the one-order harmonic (ω0). The production of one-order harmonic is ascribed to the coherent transition radiation (CTR) generated by microbunches produced in the transporting of hot electron beams. The red shift is caused by the expansion of the critical density surface. With the increase of the laser energy, the peak of the CTR moves further to the long wavelength side. Intensity of transition radiation decreases with the increase of the target thickness.