Indium phosphide (InP) has the characteristics of high electron mobility, large band gap, high temperature resistance, and radiation resistance. It is an important material of electronic devices in the space radiation environment. With the miniaturization of electronic devices, the displacement damage (DD) effect caused by a single heavy ion in the device may give rise to permanent failure. Therefore, this paper uses Monte Carlo software Geant4 to simulate the transportation process of space heavy ions(C, N, O, Fe) in InP. The non-ionizing energy loss (NIEL) of heavy ions is calculated for getting the information about displacement damage. Some conclusions are drawn as follows. 1) NIEL is proportional to the square of the atomic number, which means that single Fe can make severe displacement damage in InP. 2) The heavy ions NIEL is 3 to 4 orders of magnitude larger than PKA NIEL. The NIEL is proportional to the non-ionizing damage energy of recoil atoms produced by nuclear elastic collision, which indicates that the primary recoil atoms produced by heavy ions are the main cause of InP DD. 3) The number of heavy ions in space is small, so the proportion of total non-ionizing damage energy produced by heavy ions in 0.0125 mm³ InP is only 2.56% in one year. But the NIEL of heavy ions NIEL is 2–30 times that of protons and α particles, so the DD effect caused by single heavy ion incident on InP electronic device still needs to be considered. 4) NIEL decreases slightly with the increase of material thickness. The reason is that low-energy heavy ions are completely deposited in the front of InP, resulting in a non-uniform distribution of non-ionizing energy deposited in the material. Analyzing the dependence of mean DD energy with depth, we find that mean DD energy decreases with incident depth increasing, which means that the most severe DD region of heavy ions in InP is in the front of material.