The kinetics of nonisothermal crystallization in a novel microbial synthesis of a biodegradable block copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(HB-co-HV), in which the mole fractions of 3HV units are 7 and 10 mol%, were studied by differential scanning calorimetry (DSC). The kinetics of the block copolymer under nonisothermal crystallization conditions was analyzed by Ozawa's equation using three different methods. The comparison of nonisothermal crystallization of the block P(HB-co-HV) copolymer, homopolymer polyhydroxybutyrate, PHB, and random P(HB-co-HV) copolymer, in which the mole fractions of 3HV units are 6 and 12 mol%, was performed. It was found that the n values of the block P(HB-co-7% HV) and block P(HB-co-10% HV) are the same as that of PHB, and have been found to be close to 3. The n values of the random P(HB-co-6% HV) and random P(HB-co-12% HV) have been found to be close to 1. It was obvious that the nonisothermal crystallization rate of block polymers was faster than that of random polymers.