An automatic sintering mechanism of a multiplier tube nozzle comprises a workbench, a first clamping mechanism, a second clamping mechanism and a sintering mechanism, wherein a sliding platform is arranged at the upper end of the workbench, the sintering mechanism is installed on the sliding platform, and an auxiliary mechanism is installed beside the sliding platform; the first clamping mechanismcomprises a rotating assembly and a first clamping assembly, the rotating assembly is mounted on the sliding platform, and the first clamping assembly is fixedly connected with the rotating assembly;the second clamping mechanism comprises a moving assembly and a second clamping assembly, and both the moving assembly and the second clamping assembly are installed on the sliding platform; and thesintering mechanism comprises a driving assembly and a sintering assembly. The automatic sintering mechanism has the beneficial effects that the reliance on experience of operators is reduced, new employees can be competent for the job after simple training and produce productivity, the consistency of product appearance and quality is improved, the sintering efficiency is more than ten times thanthat of manual sintering, the rate of finished products reaches 99.99%, the automation degree is high, and more than 70% of labor is saved.