The invention discloses a preparation method for a planar-type oxygen sensor based on a femtosecond laser composite technology. The preparation method comprises the steps that firstly, nanosecond, picoseconds or femtosecond laser are selected as original laser to conduct scan, sinter and melt according to the accuracy requirement of each layer of the oxygen sensor, and then picoseconds or femtosecond laser are selected to conduct finish machining on specific areas according to real-time monitoring feedback. According to the actual requirement of the oxygen sensor, the real-time monitoring can be size detection, crystal structure detection, surface appearance detection, composition detection and the like. According to the preparation method for the planar-type oxygen sensor based on the femtosecond laser composite technology, more precise size control and resistance value control can be achieved, the technology is simpler, following resistance repairing is not needed, the precision can be reached without compensation, the processes like clearing and polishing needed when the normal 3D printing is finished are left out, and the problems that the powder is blown, the residual stress is high, and the strength is low are solved; at the same time, excellent uniformity is achieved.