A data writing method, a valid data identifying method and a memory storage apparatus using the same are provided. The method includes receiving first data; using a first programming mode to write first sub-data of the first data into a first physical programmed unit of at least a first memory sub-module of a plurality of memory sub-modules, wherein a size of each of the first sub-data is the same as a preset size; and using a second programming mode to write remaining sub-data of the first data into a second physical programmed unit of a second memory sub-module of the plurality of memory submodules, wherein the size of the remaining sub-data is less than the preset size, and the second memory sub-module is different from a third memory sub-module of the first memory submodules which is a last memory sub-module for writing the first sub-data.