A rail terminal assembling structure comprising: a protection member having a contact side section, a connection side section opposite to the contact side section and two lateral sections, the contact side section, the connection side section and the lateral sections together defining an assembling passage passing through the protection member, the assembling passage having a wire inlet, at the junction between the connection side section and each of the two lateral sections, the wire inlet being formed with a first locating section, a second locating section being disposed distal from the first locating section; a conductive plate, one end of the conductive plate extending into the assembling passage of the protection member and securely attaching to an inner surface of the contact side section; and a metal leaf spring having a first section, a second section and an elastic bight section connected between the first and second sections (31, 32), two first located sections are respectively disposed on two sides of the first section of the metal leaf spring near the middle of the first section, the metal leaf spring extending into the assembling passage and attaching to the connection side section, whereby the two first located sections are snugly securely connected with the first locating sections, a second located section being disposed near or at the tail end of the first section, the second locating section being cooperatively securely connected with the second located section, the second section of the metal leaf spring extending toward the contact side section to press the conductive plate, characterized in that: the two lateral sections are disposed between the connection side section and the contact side section; the metal leaf spring is a substantially U-shaped member; the second locating section is disposed at one end of the protection member and the second locating section is at least one protruding elastic locating section disposed on the connection side section of the protection member, the second located section being a locating hole formed on the first section of the metal leaf spring corresponding to the elastic locating section, whereby the metal leaf spring itself can be securely connected with the protection member. a protection member having a contact side section, a connection side section opposite to the contact side section and two lateral sections, the contact side section, the connection side section and the lateral sections together defining an assembling passage passing through the protection member, the assembling passage having a wire inlet, at the junction between the connection side section and each of the two lateral sections, the wire inlet being formed with a first locating section, a second locating section being disposed distal from the first locating section; a conductive plate, one end of the conductive plate extending into the assembling passage of the protection member and securely attaching to an inner surface of the contact side section; and a metal leaf spring having a first section, a second section and an elastic bight section connected between the first and second sections (31, 32), two first located sections are respectively disposed on two sides of the first section of the metal leaf spring near the middle of the first section, the metal leaf spring extending into the assembling passage and attaching to the connection side section, whereby the two first located sections are snugly securely connected with the first locating sections, a second located section being disposed near or at the tail end of the first section, the second locating section being cooperatively securely connected with the second located section, the second section of the metal leaf spring extending toward the contact side section to press the conductive plate, characterized in that: the two lateral sections are disposed between the connection side section and the contact side section; the metal leaf spring is a substantially U-shaped member; the second locating section is disposed at one end of the protection member and the second locating section is at least one protruding elastic locating section disposed on the connection side section of the protection member, the second located section being a locating hole formed on the first section of the metal leaf spring corresponding to the elastic locating section, whereby the metal leaf spring itself can be securely connected with the protection member. the two lateral sections are disposed between the connection side section and the contact side section; the metal leaf spring is a substantially U-shaped member; the second locating section is disposed at one end of the protection member and the second locating section is at least one protruding elastic locating section disposed on the connection side section of the protection member, the second located section being a locating hole formed on the first section of the metal leaf spring corresponding to the elastic locating section, whereby the metal leaf spring itself can be securely connected with the protection member.