The measurement of vitrinite reflectance (R

o

) is of great significance to the determination of its maturity and evolution of organic matters. Referring to the studies by D. W. Waples (1980) and combining the practical data from Sichuan and Guizhou

the author thinks that there would be such corresponding relationships between the vitrinite reflectance and the maturity of organic matters:R

o

0.65 prematured dry gas0.65—1.30 matured oil generated1.31—2.20 postmatured wet gas2.2—5.50 supermatured dry gas 5.50 unknown After analysing the vitrinite reflectance data from five coal series in Upper Permian

Lower Carboniferous

Lower Permian

Upper Triassic and Neogene respectively

it is discovered that R

0

for the T

s

is 0.4%—1.47%

for P

2

0.75%—4.08% and for C

1

2%.In Upper Permian

the lateral veriations of vitrinite reflectance are as follows:1. 0.75%≤R

o

1.30%

corresponding to matured zone

mainly distributed in areas of east and west Guizhou;2. 1.30%≤R

o

2.20%

corres

ponding to postmatured zone

mainly distributed in central Guizhou.3. 2.20%≤R

o

4.10%

corresponding to supermatured zone

mainly located in the north and southwest of Guizhou.In the first two areas mentioned above

there exist oil seepages and soft bitumens but only carbonaceous bitumens in the third area.Results are calculated according to the vitrinite reflectance that the palaeotemperature of the Upper Permian in Guizhou was 90°—215℃

and its ancient geothermal gradient was 19.5°—48.2°C/km. By the analysis of thermal evolution of organic matters in Upper Palaeozoic sediments

one may consider that the Palaeozoic sediments in most areas of Guizhou once were buried at the depth of 5

000—13

000m

that's why the maturity of organic matters.there is very high

and the vitrinite reflectance in some place is even greater than 5.5%. Therefore

oil prospects in Palaeozoic sediments in Guizhou is not perspective

but it is better prospect in gas expioration.