For fast and stable packaging of superconducting nanowire single photon detector (SNSPD), a self-aligned packaging method is developed that directly couples the optical fiber and the photosensitive area of the device. First, the SNSPD devices based on the dielectric mirror structure are fabricated by semiconductor micro-nano processing technology. The double-sided exposure and deep silicon etching technology are used to prepare the SNSPD chips, whose size matches well with the fiber sleeves. Then the main packaging structure including optical fiber sleeve, PCB, zirconia ferrule, etc. are glued together and packaged with the SNSPD chips. Finally, the self-aligned SNSPDs are characterized at the temperature of 2.2 K. The optimal result is 93.7% of detection efficiency at 1550 nm. The stability of the self-aligned SNSPD is verified by repeated experiments. The results show that the standard deviation of the device efficiency fluctuation is within ±0.60% in the case of repeated temperature rise and fall. The standard deviation of the device efficiency fluctuation is ±1.80%, and the maximum is 3.24% in the case of repeated insertion and extraction of optical fibers. Experimental results show that the self-aligned SNSPD has good stability, and this packaging method is expected to provide a reference for the future SNSPD packaging mode and provide early exploration possibilities for its integration and commercialization.