We controllably synthesized CH3NH3PbBr3 quantum dots with a tunable spectrum with the emission peaks covering the range from green (523.6 nm), to blue and eventually to deep violet (432.9 nm), which is wider than that of quantum dots obtained without changing the halide component. The mechanism of photoluminescence spectral blueshift of CH3NH3PbBr3 quantum dots was investigated. The CH3NH3PbBr3 quantum dots with 5–30 μL n-octylamine showed an ideal color-saturated green emission and a narrow full width at a half-maximum of 19–24 nm. The photoluminescence quantum yielded up to 90.2%. All these properties indicate that these quantum dots can provide the effective data support for application to white LEDs, and may potentially be used as single-component multicolor-emitting materials, which can be applied to lighting and display technology.