A photo-rheometer with a UV-cure monitoring accessory was used to measure the gelation time and volume shrinkage of acrylate/liquid crystal syrups during photopolymerization, and the volume shrinkage data were compared with those obtained from density approaches. The experimental results show that gelation times of these syrups are shorter than 10 s and the volume shrinkages are alomost the same via the different test approaches, which implies the photo-rheology (P-Rheology) technique is an accurate and easy method to measure online photopolymerization volume shrinkage of acrylate/liquid crystal systems. Two types of polyhedral oligomeric silsesquioxane (POSS), methacrylisobutyl polyhedral oligomeric silsesquioxane (MI-POSS) and methacryl polyhedral oligomeric silsesquioxane (MA-POSS), were added to acrylate/liquid crystal syrups in order to reduce their volume shrinkage during photopolymerization. P-Rheology and photo-differential scanning calorimetry (P-DSC) were used to investigate the effects of POSS content and type on volume shrinkage and double-bond conversion of acrylate/liquid crystal syrups, respectively. The results indicate that MA-POSS slightly decreases the double-bond conversion while does not bring obvious effect on the volume shrinkage. Adding 10 wt% MA-POSS only declines the photopolymerizion volume shrinkage by 12%. However, MI-POSS does not change the double bond conversion while can reduce markedly the volume shrinkage. The photopolymerizion volume shrinkage of acrylate/liquid crystal syrups is decreased by 29% with adding 10 wt% MI-POSS.