A microspore is haploid.
Gymnosperms are heterosporous, and therefore create two types of spores: male and female -- microspores and megaspores, respectively. These spores will develop into gametophytes which then undergo fertilization (i.e., the male/female gametophytes combine their chromosomes). To avoid constantly increasing the chromosome number of these plants, these gametophytes (and therefore the male/female spores), must only contain half of the "proper" number of chromosomes. In other words, these male/female structures must be haploid (1n). Haploid cells develop via meiosis, a process in which cells essentially split twice even though their chromosomes have only been duplicated (replicated) once. In a diploid cell, this means that the resulting cells (4 of them per parent) have only 1/2 the chromosomes as the mature organism.