With the aim to synthesise well proportioned disperse poly(vinyl chloride) (PVC)/nanometre calcium carbonate (nano-CaCO3) composites, the authors used emulsifier tx10 polyoxyethylene octylphenol ether to prepare emulsion liquid for modifying nano-CaCO3. Let nano-CaCO3 well proportionedly disperse into the water, the authors created a new method for the characterisation of emulsion liquid and use the emulsion to synthesise PVC/nano-CaCO3 composite. The microstructure, particle size distribution and thermal properties of composite were respectively evaluated by TEM, laser particle size analyser and thermogravimetry analysis tests. The results showed that nano-CaCO3 were uniformly distributed in the PVC with 5·2 wt-%. Compared with the pristine PVC, the particle size distribution of the composite is more uniform and the thermal stability increases.