Photoassociation (PA) of cold atoms is a key tool widely used for accurate determination of long-range molecular potentials,measurement and tuning of interatomic interactions,as well as creation of desired cold molecules.We report the observation of PA spectra of ultracold ytterbium (Yb) atoms at the 1S0-3p1 inter-combination line by detecting the resonant loss of atoms trapped in a crossed far-off-resonance trap (crossed-FORT).Eight vibrational levels in the 10u+ molecular state are observed for PA laser detunings up to 1 GHz with respect to the atomic resonance.The photoassociation resonances have a Lorentzian shape and sub-MHz linewidths due to the ultra low temperature of the atoms,and the resonance positions agree well with that predicted by the semiclassical formula.