Tapered and lensed fiber(TLF) is the key device to couple optical energy from optical fiber into planar lightwave circuits(PLC) high-efficiently. To understand and grasp TLF's focusing performance is pivotal for PLC pigtail packaging technology. The theoretical analysis model of output beam spot diameter and far-field divergence angle, which are principal parameters to represent TLF's focusing characteristics, is put forward. The error of the model falls within 1.14%. Lightwave propagation and mode field evolution are simulated by finite-difference beam propagation method so that the spot diameter is ascertained. TLF's taper length , half core taper angle, and lens curvature radius are optimized to be 300 μm, 0.733°, 13.485 μm respectively. The focusing beam spot is observed by digital video camera experimental setup and calculated using an inverse deducing method from physical optics. The theoretical and measurement results are consistent. For a specific TLF sample, the spot diameter value by inverse deducing method is differed from the theoretical one with error of 3.15%, and the error for far-field divergence angle is 3.67%.