The invention provides an append operation method for an LSM tree memory system. The append operation method comprises following steps of: 1), constructing value to be appended and a key to be appended to be in a key-value structural body and utilizing a newly-constructed key-value structural body as latest data segments of the key to be appended for storage in a database; saving aggregate data amount of accumulated data segments before the key to be appended as for the newly-constructed key-value structural body and saving a storage position of a data segment before the key to be appended; and 2), updating table items of the key to be appended in the append table which records aggregate data amount of all data segments of all keys and storage positions of latest data segments. The invention further provides a reading and merging method for corresponding loads of append operation. The append operation method for the LSM tree memory system and the reading and merging method for loads of append operation have following beneficial effects: increase in system cost is avoided due to a read-write amplification problem of append operation; during the course of moving from a lower level to a higher level, loads of append operation are aggregated; and reading performance of loads of append operation can be improved.