When a business expands through acquisitions or upgrades its brand architecture, it often needs to consolidate 3–5 previously separate subsidiary/division websites under one new main group website. From a technical and SEO perspective, this is a high-risk “heart bypass operation”: if all the subsidiaries' old domains are simply redirected to the group homepage in a single sweep, the long-tail product keyword rankings each subsidiary has built over many years will be wiped out within two weeks.

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1. Wrong approach vs. right approach: never redirect everything to the homepage

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Search engines (Google and Baidu) apply a clear algorithmic criterion to cross-domain 301 redirects: an old page's ranking authority will transfer successfully to the new page only when their content topics are closely equivalent. If subsidiary A's “laser cutting machine model detail page” is redirected directly to the group's “main homepage” with a 301, search engines will classify it as a Soft 404 and discard the page's existing ranking authority.

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2. The “four-step lossless migration method” for consolidating multiple websites

  1. Step 1: create equivalent division/product-line subdirectories on the main group website Plan clear destination sections under the group's primary domain for each former subsidiary's core business (for example, all products formerly on sub-a.com move to group.com/laser-systems/, while the business formerly on sub-b.com moves to group.com/automation/). Prominently state on the division landing page that “The former XX Company has now become the Intelligent Equipment Division of XX Group” to help existing customers feel familiar with the new website.
  2. Step 2: create a “one-to-one URL mapping table (Redirect Map)” Use a crawler to export all URLs on each subsidiary's website that are currently indexed, receive organic search clicks, or have inbound external links, and build a rigorous mapping table:
    • sub-a.com/products/model-x ──(301 permanent redirect)──> group.com/laser-systems/model-x
    • sub-a.com/about ──(301 permanent redirect)──> group.com/about#subsidiaries
    • Only 301-redirect the old homepage sub-a.com/, where there is genuinely no corresponding internal page, to the relevant division homepage on the group website.
  3. Step 3: submit a “change of address” in Google Search Console and Baidu's webmaster platform Do not stop after configuring Nginx redirects on the server. You must log in to the webmaster platforms for each former subsidiary domain and the new group domain, and submit them for official verification using GSC's Change of Address tool and Baidu's Website Migration tool (site consolidation rules).
  4. Step 4: maintain the old domains' DNS resolution and SSL certificates for at least 1–2 years A 301 redirect depends on the old domain continuing to resolve correctly and having a valid HTTPS certificate (if the old domain's SSL certificate expires and produces an error, the browser will block the request before the redirect). Be sure to keep renewing the old domains and certificates for at least 12–24 months, until 100% of the ranking authority has been transferred.