Electrons are an important constituent part of radiation space of charged particles and could damage microelectronic devices. Therefore, effective radiation protection is very important for the electronic device. So, a radiation protecting material with lightweight, high performance and low cost is urgently needed. Polyethylene (PE) with high hydrogen content/carbon nanotube (CNT) composite as a space shielding material is very promising for spacecraft application in the future. In order to meet the requirement of space applications for PE/CNT composite, it is of important academic value and practical significance to explore melting and crystallization behaviors of LDPE/MWCNT composites. In this paper, melting and crystallization behaviours of the irradiated LDPE/MWCNT composites irradiated by 110 keV electrons are studied by differential scanning calorimetry (DSC), synchrotron radiation X-ray small angle scattering (SAXS) and wide angle diffraction (WAXD). Experimental results show that the irradiation by 110 keV electrons does not affect the thermal characteristics of the LDPE, but can enhance the initial melting temperature and the melting-terminating temperature of LDPE/2% MWCNT composites during melting. Also, the radiation by 110 keV electrons could reduce the initial crystallization temperature and the crystallization-terminating temperature during crystallization. MWCNTs could enhance the initial melting temperature and reduce the melting-terminating temperature of LDPE/2% MWCNT composites during melting. Moreover, MWCNTs could enhance the initial crystallization temperature and crystallinity, and reduce the crystallization-terminating temperature during crystallization. SAXS and WAXD analyses show that with increasing the temperature, long periods of the irradiated/unirradiated LDPE increase during melting. Compared with that of the unirradiated LDPE, at a given temperature, long period of the irradiated LDPE is small. During crystallization, with reducing the temperature, long period of the irradiated/unirradiated LDPE begins to appear and gradually decreases. At the same temperature, long period of the irradiated LDPE is larger than that of the unirradiated one. For LDPE/2% MWCNT composites, long periods of the irradiated/unirradiated samples during melting and crystallization do not exist. The 110 keV electron irradiation mainly influences LDPE matrix of LDPE/2% MWCNT composites during melting and crystallization. The 110 keV electron irradiation can slow down the amorphous region expansion and the initial melting of lamellae of the LDPE matrix during melting. The 110 keV electron irradiation can slow down the amorphous region shrinkage and inhibit crystal from growing up during crystallization. During melting, MWCNTs can hinder the amorphous and crystalline molecular chains of LDPE from moving, which hinders the LDPE matrix from initially melting, but promotes the melting process after the initial melting has begun. During crystallization, MWCNTs could promote the formation of crystal of the LDPE matrix and inhibit the crystal from growing up.