Abstract: [OBJECTIVE] Bovine Viral Diarrhoea-Mucosal Disease Virus HB strain was a field strain isolated from a dairy cows flock in HeBei province. The study were progressed in order to realize characters of HB strain, provide theory base for illuminating pathogeny and control infection and prevalence of BVDV. [METHOD] The biological characteristics of the virus HB strain were determined by Physicochemical and biological analysis methods. [RESULTS] The results indicated that the virus could be seen with typical MDV virions. By negative staining electron microscope, virions were roughly round and approximately 40-60 nm in diameter with peplomers. Density is 1.13~1.14g/cm3. The hemagglutination reaction test proved that this virus had no any reaction to erythrocyte of chook, rabbit, pig and sheep. The result of TCID50 is 10-4.5. Physicochemical assays showed that this virus was sensitive to chloroform and ether and trypsin. In acid alkali tolerance assay, the virus was sensitive to pH3.0 and resistant to pH9.0. The virus was sensitive to 56℃ for 30 minute and was inactivited by heat to 56℃ for 30 minute. It was similar to tandard strain in morphological feature, density, the chemical and physical characteristics and haemagglutinating activities. Type of nucleic acid assay indicated that virions multiply could not be inhibited by 5，-IUDR. The virus genome is RNA. Five stripes of special virus structural protein were obtained by SDS—PAGE. [CONCLUSION] Virus HB Strain was a bovine viral diarrhoea-Mucosal disease virus strains.