The invention discloses a preparation method of a platinum alloy melting crucible. The method comprises the following steps of 1, uniformly mixing calcium oxide powder and calcium carbonate powder toobtain mixed powder; 2, charging the mixed powder; fully filling a quartz crucible; 3, sealing an opening of the quartz crucible fully filled with the mixed powder; then, digging holes to the inside from the top of the quartz crucible; removing an opening sealing device to obtain a crucible blank body; 4, laying a platinum alloy sheet into the holes of the crucible blank body; then, performing heating so that the platinum alloy sheet is converted into a melt; 5, inclining the heated crucible blank body; performing resetting and reheating so that the platinum alloy is completely molten; 6, repeating the crucible blank body inclination, resetting and heating process in the step 5 until the hole inner wall of the crucible blank body is sintered to form a porcelainized layer; pouring out the platinum alloy melt to obtain the crucible. The prepared platinum alloy melting crucible has the advantages that the wet sand opening sealing on the crucible is not need; the porcelainized cracking dueto crucible opening moisture absorption is avoided; the service life of the crucible is prolonged.