IoT international standardization events launched by Standard Development Organizations (SDOs), including ITU-T, OneM2M, 3GPP, IETF and OMA were introduced. Correspondingly, the differentiated positions of these events were indicated. The main content or characteristics of several standards, i.e. ITU-T Y.2060, OneM2M, 3GPP TS 23.682, IETF 6LowPan, IETF COAP, OMA DM and OMA LightWeightM2M were concluded.