The invention discloses a low-temperature J-T (Joule-Thomson) throttling cooler precooled by a Stirling/pulse tube composite type cooler. The low-temperature J-T throttling cooler comprises a precooling unit and a cooling unit; the cooling unit comprises a J-T compressor, a primary regenerative heat exchanger, a secondary regenerative heat exchanger, a pre-throttling heat exchanger, a throttling valve and an evaporator; and the precooling unit is a secondary Stirling/pulse tube composite cooler mechanism or a higher-level Stirling/pulse tube composite cooler mechanism, and is used for precooling J-T throttling cooling circulation helium working media by cooling agents of the Stirling/pulse tube composite type cooler before the J-T throttling cooling circulation helium working media are filled into a high-temperature-side pipeline of the pre-throttling heat exchanger, and the cooling agents perform multi-level precooling for the J-T throttling cooling circulation helium working media. The cooling performance of J-T throttling cooling circulation after precooling by the Stirling/pulse tube composite type cooler is superior to that of J-T throttling cooling circulation after precooling by an existing single regenerative cooler, and the low-temperature J-T throttling cooler is high in reliability and long in service life, and has the advantages of compact structure and the like.