An anamorphic photonic crystal fiber (PCF) is introduced to improve the coupling loss between rectangular laser and conventional single-mode fiber. One end with rectangular core is connected with laser, the other end with round core connect with conventional fiber. Firstly, the coupling efficiency is calculated by beam propagation method. Then after blocking four holes of the PCF, and inflating, heating, an anamorphic core-shape PCF is formed with four holes absolutely collapsed. The simulation results show that, comparing to the straight coupling between rectangular laser and conventional single-mode fiber, more than 3.9 dB improvement of coupling efficiency is achieved by this new method. And the experimental results show that the new structure is feasible.