A new PVC-Chlorella composite material (PCCM) was investigated aiming at the effective utilization of biological CO2 fixing Chlorella. The microalga Chlorella, after fixing CO2, was molded with PVC. Molding conditions of PCCM, and physical properties of Chlorella were studied using tensile strength as an index for estimating the properties of PCCM. The optimum parameters for molding of PCCM were as follows: temperature = 180 degrees C, pressure = 4.4 MPa and time = 5 min. The following physical parameters of Chlorella best enhance high tensile strength: water content of 2%, average particle size of 30-80 mu m and a relatively homogeneous distribution of particle size. Chlorella, maintaining its original shape, exists in PCCM as an empty ball inlaid in the matrix of PVC. The PCCM shows a lower elongation and is more brittle than PVC, possibly as a result of gas and residual PVC primary particles around Chlorella grains. A comparison between theoretical and experimental results show that there is an effective combination between the PVC matrix and the Chlorella surface in PCCM. PCCM has a tensile strength higher than 30 MPa which meets the requirements for rigid PVC products, if Chlorella content is less than 20%. Chlorella can thus be effectively utilized as a practical filler.