The invention relates to a fault current analysis method of a high-voltage DC transmission system, in particular to a converter valve alternating current system 1s fault tolerance property analysis method. The method includes the steps of step 1, simulating a converter valve alternating current system alternating current side 1s fault, step 2, determining the thermal stress limit of a thyristor converter valve, and step 3, determining the maximum direct current which can pass through the thyristor valve when the 1s fault happens to the alternating current system. According to the method, the thermal stress limit of the thyristor valve is calculated in a simulation way, in addition, the maximum current that the thyristor converter valve can bear when the 1s fault happens to the alternating current system is calculated according to the limit, and therefore a basis is provided for design and operation of the converter valve.