The un-doped Mg11B2 and Cu-doped Mg11B2 bulks using 11B as a boron precursor were fabricated by solid-state reaction and sintered at different temperature in present work. By analyzing the sintering process, it was found that 11B original powder is more reactive and can react with Mg severely even at low temperature before Mg melting, which leads to the formation of refined Mg11B2 grains. Consequently, the critical current density of Mg11B2 sample prepared in this work is higher than that of natural MgB2. Furthermore, it was found that proper Cu addition could obviously accelerate the reaction between Mg and 11B and promote the formation of Mg11B2 due to the appearance of Mg-Cu liquid at low sintering temperature before Mg melting. On the other hand, Cu addition also introduced more MgCu2impurity, leading to a relatively lower critical current density on the whole. Interestingly, the critical current density of the Cu doped sample sintered at 800 °C is surprisingly enhanced at the low field, compared with that of the corresponding un-doped one. This is due to the peritectic reaction which generated small-sized MgCu2 occurred that at 800 °C, providing MgCu2 pinning centers well-distributed in the MgB2 matrix.