Hi,
Recently i have broadcasted two public subsets on two different ISPs.My inbound load sharing and fail over is working with BGP Prepend attribute.How i achieve outbound load sharing from policy base routing kindly help me out.I do not want use local perf attribute for outbound traffic reason in that my BGP in filter i am not accepting any routes from ISPs.

Might want to take a look at the Mikrotik wiki for outbound load sharing strategies [1]. Firewall marking + mangle might be the right way to go here. Exactly what to configure would require more context about what else these routers are doing (NAT/firewalling/etc.).

Presumably if you're doing BGP traffic engineering you're already aware, but I would take care to make sure that your outbound load sharing strategy matches on the same source-address prefixes as your BGP-announced prefixes. Otherwise, you might get asymmetric return traffic from the internet.

[1] https://help.mikrotik.com/docs/display/ ... +Balancing