The invention relates to a high density electric connector and a method for assembling the same. The electric connector comprising a connector base arranged on a circuit board, a plurality of terminal channels arranged on the connector base and a plurality of terminals correspondingly arranged in the terminal channels is connected with an electric device and the circuit board; the circuit board is provided with a plurality of circuit junctions; ends of the terminals, which are close to the circuit board, are provided with extension parts contacting the circuit junctions, a terminal material belt is connected with the other ends of all terminals, which are away from the circuit board. The assembling method of the invention comprises the following steps that: the connector base is taken away from a top part of the circuit board, and all terminals are inserted in the corresponding terminal channels of the connector base; secondly, the terminals are separated from the material belt; finally, terminals are connected with the circuit board. The structure of the invention avoids that the electric device is damaged due to improper plug-in and plug-out; the assembling method ensures the manufacturing accuracy of terminal, enhances the joint rate and the flatness between the electric connector and the electric junctions of the circuit board, improves the rate of products and lowers the manufacturing cost.