To improve the electrochemical performance of LiMnPO4 cathode for lithium ion battery, many efforts focus on cation doping/substitution on Mn-site. Here we synthesize a boron doped LiMnPO4 on P-site, LiMn(P0.9B0.1O4−δ ), by a simple solid-state method. It is characterized by X-ray diffraction, scan electron microscopy, cyclic voltammograph, electrochemical impedance spectroscopy and capacity testing. Results show that its electrochemical performance is improved compared with the virginal LiMnPO4. It delivers a capacity of about 130 mAh g−1 at 0.1 C and remains 71% of the capacity at high discharge rate of 2 C. After 50 cycles at 0.2 C, there is no evident capacity fading.