The specimens with straight channels and the product with complex channels were manufactured by laser powder bed fusion. The results showed that when the diameter of the channel was less than 2 mm, the remaining powder inside the channels could not be removed completely due to the shrinkage of the flow channels after fabricated. In addition, the forming quality of the top surface of the circular channels became worse, with the increase of the diameter while the forming quality and dimensional accuracy for ridge shape channels still kept better with the increase of the size of the section, since the inclination angle of the inner surface was a fixed value. Meanwhile, the semi-melted powder particles adhered to the upper region of the flow channels caused by the deep penetration of the laser into the powder in the non-forming region could be removed by abrasive flow machining, high pressure airflow or water. The test results of the laser powder bed melting product with complex flow channels indicated that there were no defects such as crack or remaining powder by X-ray and computed tomography test. And the pressure test suggested that the product with complex flow channels was not damaged or leaked when the pressure reached 2 MPa for 5 min. Finally, the processes “design-form-test” were successfully established for the products with complex flow channels.