This paper describes theoretical analyses of a new CRV (Code Rule Violation) collision detection method applicable to an optical CSMA/CD LANs. The new method is based on the ideas combining a partial response (1,0, --1) circuit with the basic CRV collision detection method; the ideas are proposed in IEEE 802.3 committee. The circuit configuration of the new method, however, is different from that proposed in IEEE 802.3 committee. First, the paper outlines the basic CRV collision detection method and shows the problem that it can't detect a collision when identical bits are continuously received. Secondly, a practical circuit configuration of the new method is introduced. To realize large optical dynamic range and stability in collision detection, the circuit is designed not to detect CRVs on noisy zero level signals caused by signal negation with partial response circuits. The calculation formulae are then derived for the basic and the new method to determine the CRV rate with and without signal collision. At a bit rate of 10Mb/s, the CRV rate with and without signal collision is then calculated for the basic and the new method. Finally, the calculation results are compared with each other, and it is clarified that the new method is an effective method to increase CRV rate when signal collision occurs.