Disclosed herein are crystalline forms of (N,N-Diethylcarbamoyl)methyl methyl (2E)but-2-ene-1,4-dioate, which is a prodrug of methyl hydrogen fumarate. Crystalline form 1, Crystalline form 2, Crystalline 3, and Crystalline form 4 are disclosed.本文揭示(N,N-二乙基胺甲醯基)甲基(2E)丁-2-烯-1,4-二酸甲酯之晶形,其為反丁烯二酸氫甲酯之前藥。揭示晶形1、晶形2、晶形3及晶形4。