A novel soybean cultivar, designated SE90345, is disclosed. The invention relates to the seeds of soybean cultivar SE90345, to the plants of soybean SE90345 and to methods for producing a soybean plant produced by crossing the cultivar SE90345 with itself or another soybean variety. The invention further relates to hybrid soybean seeds and plants produced by crossing the cultivar SE90345 with another soybean cultivar.