A novel two-step solvothermal approach was firstly applied to acquire ultrathin lithium iron (II) phosphate (LiFePO4) nanosheet (with thickness about 28 nm) with exposed (010) surface facets. The iron hydroxyl phosphate Fe3(PO4)2(OH)2 nanosheet fabricated in the first solvothermal step was proved to be effective template for ultrathin LiFePO4 formation after solvothermal lithiation in the second solvothermal step. Importantly, the two-step solvothermal lithiation could produce ultrathin nanosheets while one-step solvothermal based on Fe(II) fabrication could only produce nanoplate-like particles. The as-synthesized nanosheets has shortened Li-ion diffusion path and high robustness in the structure during high C-rate electrochemical tests. Based on comparison with bulk LiFePO4 and nano-plate LiFePO4, the LiFePO4 nanosheet exhibits quite high specific discharge capacity of 169, 165, 159, 142, and 121 mAh g−1, at C-rate of 0.1, 0.2, 0.5, 1, and 5C, respectively, and excellent cycling performance with capacity kept at 121 mAh g−1 with no obvious fading under 500 times cycles. The newly developed method can provide useful references to other olivine type LiMPO4 cathodes and even have potential to find more applications in the synthesis of functional materials.