Abstract：Ultracold molecules offer great opportunities to study molecular collisions in the quantum regime. At ultralow temperatures, the de Broglie wavelength of the collision partners is much larger than the range of molecular interaction potential, and only the lowest possible partial wave of relative orbital angular momentum dominates the collision process. Therefore, the collisions at ultracold temperatures are highly quantum mechanical. Scattering resonances are among the most remarkable quantum phenomena. They are extremely sensitive to the details of molecule interaction potential and thus offer a unique probe of the potential energy surface governing the collision dynamics. I will talk about our recent work on the observation of magnetically tunable Feshbach resonances in ultracold collisions between potassium-40 (40K) atoms and sodium-23–potassium-40 (23Na40K) molecules in the rovibrational ground state. I will also talk about our recent observation of the interference between resonant STIRAP and detuned STIRAP in creation of ground state molecules.