The invention discloses a 3D printing preparation method based on the nanosecond-picosecond-femtosecond laser compound technology for a NOx sensor and belongs to the field of NOx sensors. The 3D printing preparation method comprises the following steps: (1) laying raw material powder on a working platform and pre-heating; (2) adopting nanosecond laser to sinter and melt the raw material on the working platform, and meanwhile, adopting a real-time monitoring system to detect the precisions of all printing layer structures of a sensor; and (3) sequentially repeating the steps (1) and (2) till preparation of the NOx sensor is completed. The 3D printing preparation method has the advantages that the complex problems of powder blowing, high residual stress and the like in the conventional laser sintering process are effectively solved, and a compensation step is omitted; and more accurate size control and resistance value control are realized, the process is simpler, follow-up trimming is not needed, and better consistency is achieved.