The invention discloses a random write method and system based on an erasure code. The method comprises the steps of generating a random write file and uniquely marking the random write file and setting a file data security level of the random write file; inputting random write data in the random write file, striping the input random write data according to the erasure code and the file data security level, and calculating a random write data size and random write offset; obtaining a stripe list spanned by the random write of this time; calculating a range of data storage units of each strip needing to be updated and updating the data storage units in the range; and asynchronously recalculating and writing check data of all stripes updated by the random write file. The method and the system have the beneficial effects that when data write is carried out on the data storage units of the stripes, only partial data storage units are updated, and it is unnecessary to read the data of the whole stripes for updating, so calculation loads are reduced, and the random write amplification problem is solved by asynchronously recalculating the check data.