The high-temperature and high-pressure synthesis device comprises an outer salt
pipe, an inner salt
pipe and
pyrophyllite, the
pyrophyllite is provided with through holes used for assembling the outer salt
pipe and a conductive steel ring, the outer salt pipe is arranged in the
pyrophyllite, a carbon pipe is assembled in the outer salt pipe, the inner salt pipe is assembled in the carbon pipe, a
metal cup is placed in the inner salt pipe, and the
metal cup is placed in the conductive steel ring. The upper end and the lower end of the through hole of the pyrophyllite are provided with the carbon plates and the conductive steel rings, and the carbon plates are attached to the outer salt pipe, the carbon pipe, the inner salt pipe and the salt plates. During application, the carbon tube simultaneously heats the inner salt tube and the outer salt tube to simultaneously generate two isostatic pressing areas formed by
molten salt, namely an inner isostatic pressing
pool and an outer isostatic pressing
pool, and the inner isostatic pressing
pool provides a
hot isostatic pressing environment which is suitable for
sintering the
diamond hard
alloy compact and has equal pressures in all directions; the outer isostatic pressing tank provides a pressure environment with uniform stress for the carbon tubes in the outer isostatic pressing tank, and the stress of the carbon tubes is balanced; and the
sintering quality of the
diamond hard
alloy compact is obviously improved.